Method of treating optical film, apparatus of treating optical film, and method of manufacturing optical film

ABSTRACT

An object of the present invention is to provide a method of treating an optical film wherein coating defects such as chatter, coating streaks and comet failure which are easily caused, when coating a functional layer such as an anti-reflection layer on a long-length film, are improved, as well as an apparatus of treating an optical film. Disclosed is a method of treating an optical film possessing the steps of rubbing a long-length film transported with elastomer moisturized with liquid, and removing the liquid on a surface of the long-length film, wherein an elastomer surface has a static friction of 0.2-0.9.

This application claims priority from Japanese Patent Application No. 2005-206875 filed on Jul. 15, 2005 and Japanese Patent Application No. 2005-242448 filed on Aug. 24, 2005, which are incorporated hereinto by reference.

TECHNICAL FIELD

The present invention relates to a method of treating an optical film wherein easily generated coating defects such as chatter, a coating streak and comet (comet failure) when coating a functional layer such as an anti-reflection layer on a long-length film, are improved, a apparatus of treating the optical film and a manufacturing method for the optical film, and in particular, to a method of treating an optical film, a apparatus of treating an optical film and a manufacturing method for an optical film which improve chatter.

BACKGROUND

With advanced development of a thin and light lap-top type personal computer and a thin and large-sized television in recent years, a protective film of a deflecting plate used in a display device such as a liquid crystal display device is strongly requested to be more thinner, larger and to be of a higher performance. Further, there has become popular a liquid crystal image display device (liquid crystal display) such as a computer and a word processor having an optical film on which an anti-reflection layer is provided or an anti-glare layer that scatters reflected light with a roughened surface is provided for improving visibility.

The anti-reflection layer has been improved in terms of the number of types and performances to comply with applications, and various front plates having these functions are stuck on polarizers of a liquid crystal display, thereby, there is used a method to give anti-reflection functions to the display for improving visibility (for example, see Patent Document 1). On the optical film used as these front plates, there is often provided an anti-reflection layer that is formed through a coating method, an evaporation method or a sputtering method.

Further, because of the trend of a thinner display device, a layer thickness of the film to be used is requested increasingly to be thinner, or because of the trend of a larger screen, the optical film is requested to be broader. In particular, in the large screen, the optical film excellent in flatness is desired. However, in the case of a conventional optical film, it is not possible to obtain a broad and thin optical film that is excellent in flatness, and sufficient anti-scratch ability has not been obtained under the condition of a broad area.

When coating a metal oxide layer as an anti-reflection layer, in particular, coating defects tend to be caused, and its improvement has been demanded. When a width of a base material film is as wide as 1.4 m or more, in particular, coating defects tend to be caused extremely, and improvements for chatter, coating streaks and comet have been demanded.

[Patent Document 1] Japanese Patent O.P.I. Publication No. 2002-182005

SUMMARY

It is an object of the present invention to provide a method of treating an optical film wherein coating defects such as chatter, coating streaks and comet which are easily caused, when coating a functional layer such as an anti-reflection layer on a long-length film, are improved, as well as an apparatus of treating an optical film. Disclosed is a method of treating an optical film possessing the steps of rubbing a long-length film transported with elastomer moisturized with liquid and removing the liquid on a surface of the long-length film, wherein an elastomer surface has a static friction of 0.2-0.9.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements numbered alike in several figures, in which:

FIG. 1 is a pattern diagram showing the whole of the device that rubs the surface on one side of the long-length film transported continuously by elastomer moisturized with liquid of the present invention,

FIG. 2 is a pattern diagram showing another example of the device that rubs the surface on one side of the long-length film transported continuously by elastomer moisturized with liquid of the present invention,

FIG. 3(a) is a diagram of principle showing a measuring method of the static friction factor,

FIG. 3(b) shows a tear-off test specimen and the measuring direction,

FIG. 3(c) shows a cross-sectional view of a test specimen and a tear-off section,

FIG. 4(a) and FIG. 4(b) each show a liquid tank connected with a rinse nozzle placed at a different position through piping,

FIG. 4(c) shows an example of liquid jetted on the film surface by a rinse nozzle,

FIG. 5(a) shows a cleaning process of using an ultrasonic transducer,

FIG. 5(b) shows a cleaning process of using a blade,

FIG. 5(c) shows a cleaning process to rub with another elastomer such as a rubber roller,

FIG. 5(d) is a cleaning process showing an installation position of an air nozzle, and any position can be used for installation,

FIG. 6(a) shows that air is sprayed in the direction against the film traveling direction,

FIG. 6(b) and FIG. 6(c) each show that air is sprayed toward the outside of the film, and

FIG. 6(d) and FIG. 6(e) each show an example suitable for each of air nozzles installed on the opposite side of the treated surface of a film.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The above object of the present invention is accomplished by the following structures.

(Structure 1) A method of treating an optical film possessing the steps of rubbing a long-length film transported with elastomer moisturized with liquid and removing the liquid on a surface of the long-length film, wherein an elastomer surface has a static friction of 0.2-0.9.

(Structure 2) The method of Structure 1, wherein the elastomer is a surface-modified rubber.

(Structure 3) The method of Structure 1 or 2, further possessing a step of adjusting a transporting position by detecting an end position of width of the long-length film.

(Structure 4) The method of any one of Structures 1-3, wherein a temperature of the liquid is in a range of 30-100° C., and a temperature of the elastomer is in a range of 30-100° C.

(Structure 5) The method of any one of Structures 1-4,

wherein the long-length film is rubbed with the elastomer while pressing a back surface of the long-length film.

(Structure 6) The method of any one of Structures 1-5, wherein before the long-length film is rubbed with the elastomer moisturized with the liquid, a treated surface of the long-length film is moisturized with liquid in advance.

(Structure 7) The method of Structure 6, wherein the treated surface is moisturized with a device of supplying liquid onto the treated surface of the long-length film.

(Structure 8) The method of Structure 6 or 7, further possessing a step of supplying liquid between the long-length film and the elastomer.

(Structure 9) The method of any one of Structures 1-8, wherein a period of time during which the treated surface is moisturized is in a range of 2-60 sec.

(Structure 10) The method of any one of Structures 1-9, wherein the long-length film has a thickness of 30-70 μm.

(Structure 11) An apparatus of treating an optical film possessing a device of rubbing a long-length film transported with elastomer moisturized with liquid, and a device of removing the liquid on a surface of the long-length film, wherein an elastomer surface has a static friction of 0.2-0.9.

(Structure 12) The apparatus of Structure 11, further possessing a device of adjusting a transporting position by detecting an end position of width of the long-length film.

(Structure 13) The apparatus of Structure 11 or 12, further possessing a device of adjusting a temperature of the liquid to 30-100° C. and a device of adjusting a temperature of the elastomer to 30-100° C.

(Structure 14) The apparatus of any one of Structures 11-13, further possessing a device of pressing a back surface of the long-length film.

(Structure 15) The apparatus of any one of Structures 11-14, further possessing a device of moisturizing a treated surface of the long-length film with liquid in advance before rubbing the long-length film.

(Structure 16) The apparatus of Structure 15, wherein the device of moisturizing the treated surface is a device of supplying liquid onto the treated surface of the long-length film.

(Structure 17) The apparatus of Structure 15 or 16, wherein the device of moisturizing the treated surface is a device of supplying liquid between the long-length film and the elastomer.

(Structure 18) The apparatus of any one of Structures 11-17, wherein a treating time between a starting point of moisturizing the treated surface with a device of moisturizing the treated surface and a termination point of removing the liquid with a device of removing the liquid is in a range of 2-60 sec.

(Structure 19) A method of manufacturing an optical film, comprising a step of coating a functional layer onto the treated surface of the long-length film after conducting treatment via the method of any one of Structures 1-10.

(Structure 20) The method of Structure 19, wherein the functional layer is an anti-reflection layer or an actinic radiation curable resin layer.

(Structure 21) The method of Structure 20, wherein the long-length film is a cellulose ester film, and the liquid is water.

While the preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Next, the present invention will now be described in detail referring to examples, however, the present invention is not limited thereto.

After rubbing a long-length film transported with elastomer moisturized with liquid, following the strenuous studies, the inventors of the present invention found amazing effects that easily generated coating defects such as chatter and coating streaks when coating a functional layer such as an anti-reflection layer on a long-length film are improved by a method of treating an optical film characterized by the static friction factor on the elastomer surface ranging from 0.2 to 0.9, in a method of treating an optical film for removing a liquid on the long-length film surface, to achieve the present invention. Incidentally, it is preferred that the atmospheric pressure plasma treatment described in U.S. Pat. No. 6,512,562 is further carried out, before or after conducting the above-described treatment of an optical film in the present invention.

The inventors of the present invention found that wrinkles, distortions and strains on the long-length film can be corrected by rubbing a long-length film with elastomer moisturized with liquid, and by letting the long-length film to pass through a step for removing a liquid sticking to the surface of the long-length film, thus, flatness of the long- length film is improved, and coating defects in the case of coating a functional layer such as an anti-reflection layer through a hard coat layer are improved.

The present inventors further found that effects of the present invention are further enhanced under the conditions that a device to adjust a transporting position by detecting an end position of width of the long-length film is provided, the foregoing liquid temperature is in a range of 30-100° C., a temperature of the aforesaid elastomer is in a range of 30-100° C., the long-length film is rubbed with the elastomer while pressing a back surface of the long-length film, and only the treated surface of the long-length film is moisturized with liquid in advance before the long-length film is rubbed with the elastomer moisturized with the liquid.

Next, the present invention will be explained in detail.

The present invention will be explained employing FIGS. 1-6, but the present invention is not limited thereto.

FIG. 1 is a pattern diagram showing the whole of the device that rubs the surface on one side of the long-length film transported by elastomer moisturized with liquid. After being rubbed, Long-length film F is guided by guide roller 2, and is rubbed by driven elastomer 1 (elastomer roll). Driven elastomer 1 is constantly kept to be wet by liquid 4 pooled in liquid tank 3. After being rubbed by elastomer, long-length film F is transported by guide roller 2′, and excessive liquid and foreign materials are blown away and removed by air coming from air nozzle 6. It is preferable that a liquid blown away is collected in liquid receiver 11 to be disposed. It is further preferable that air nozzle 5 is arranged on the side facing elastomer 1, and over-flow of liquid to back side of the film is prevented by air jetting. Further, by adjusting air pressure of air nozzle 5, a degree of pressure contact of the long-length film with the elastomer can be controlled, and it is preferable that the back surface of the long-length film is rubbed with the elastomer while adjusting and applying air pressure. As a device for the foregoing, it is possible to use either the air nozzle or a back roll. However, the use of air nozzle 5 is preferable from the viewpoint of preventing over-flow of liquid to back side of the film, as stated above. Then, the long-length film is transported to dryer 7 where both surfaces of the long-length film are dried, and is transported to the succeeding process representing the coating process for the functional layer.

Guide rollers 2 and 2′ guide long-length film F for its traveling. In this case, each of guide rollers 2 and 2′ is arranged at its prescribed position, and what is important in this case is that the long-length film is guided so that long-length film F may come into contact with elastomer 1 at a wrap angle which will be explained later, and the same surface may come close to succeeding air nozzle 6.

Elastomer 1 is arranged between guide roller 2 and guide roller 2′ and is driven by an unillustrated motor to rotate. A lower portion of this elastomer 1 is immersed in liquid 4 arranged in liquid tank 3. Long-length film F is rubbed continuously by this rotating elastomer 1 and wrinkles, distorsions and strains on the surface are corrected.

Incidentally, for elastomer 1, it is preferable that its lower portion is immersed in liquid 4, and when the elastomer rotates, its surface is constantly in the state moisturized by liquid 4. Due to this, it is considered that wrinkles, distorsions and strains on the surface can be corrected easily.

It is preferable to provide a device to supply liquid to a surface of the elastomer because the surface of the elastomer is made to be in the moisturized state, and as a liquid supply device, there is given a liquid jetting device.

In another embodiment, a surface of the elastomer may also be moisturized by jetting directly to elastomer 1 as shown in FIG. 2, and it is also possible to provide a liquid reservoir tank that collects jetted liquid, at the lower portion as shown in the same drawing. In this case, on the lower portion of the elastomer, it is also possible to clean by rubbing with a blade, a brush or a non-woven fabric, to remove contamination and deposit on the elastomer surface. This method is preferable, because adhesion of contamination and foreign materials on elastomer 1 caused by contamination of the liquid tank can be reduced.

Further, it is preferable that a liquid is coated on the treated surface of the long-length film before rubbing continuously with a moisturized elastomer, in the present invention. It is possible to moisturize in advance before rubbing the long-length film with the elastomer, by bringing guide roller 2 in FIG. 1 into contact with a liquid or immersing it in a liquid. In this case, however, a back surface of the long-length film is also moisturized, which sometimes results in generation of a watermark or slippage between the film and rollers. In the present invention, it is preferable that only treated surface is moisturized in advance, and it is preferable, from the viewpoint of preventing generation of scratches caused by foreign materials, that nozzle 8 of a device of supplying liquid in FIG. 1 is arranged between guide roller 2 and elastomer 1, and a liquid reserved in liquid tank 3 is filtered by barrier filter 10 connected with piping to be jetted from nozzle 8 through pressure pump 9, and thereby, the treated surface on the long-length film is moisturized in advance. For nozzle 8, it is possible to use either single bar-shaped nozzle having a length equal to the film width or plural short type ones. With respect to an aperture diameter of the nozzle, it is not limited in particular, but its range of about 05 mm-2 mm is preferable, and an amount of liquid to be sent ranging from 5 L/min to 50 L/min is preferable. FIG. 5(d) is one showing an installation position of air nozzle 8, and any position between 8 a and 8 e can be used for installation. Further, plural air nozzles may also be installed.

In the meantime, elastomer 1 may rotate either forwardly or inversely for the direction of transporting long-length film, and it is preferable to establish a diameter and a rotational speed of the elastomer so that an absolute value of a linear speed difference between elastomer 1 and long-length film F may be kept to be 5 m/min or more. The rotational speed in a range of 1-100 rpm is preferable, and that of 5-60 rpm is more preferable.

The transporting speed for long-length film F in the case of conducting treatment of the present invention is usually 5-200 m/min, and it is preferably 10-100 m/min.

Elastomer 1 in the form of roll is suitable for a continuous production. Elastomer 1 may be made of natural rubber, synthetic rubber or such as a single material, and may also be made of a composite material such as a metal roll, rubber and others. Examples are a metal roll such as aluminum, iron, copper or stainless steel; polyamide such as 6-nylon, 66-nylon or copolymer nylon; polyester such as polyethylene terephthalate, polybutylene terephthalate or copolymer polyester; polyolefin such as polyethylene or polypropylene; polyvinyl halide such as polyvinyl chloride, polyvinylidene fluoride or TEFLON (Registered trademark); natural rubber, neoprene rubber, nitrile rubber, NORDEL, viton rubber, HYPARON, polyurethane, RAYON (Registered trademark), cellulose, and the like. These examples each can be coated at least 0. 55 mm onto the surface of a metal roll, preferably 0.5-100 mm, and more preferably 1.0-50 mm. It is preferred that these materials are not softened or eluted depending on the utilized liquid in view of selection of material quality of these elastomers. Rubber hardness of elastomer 1 is measured by a method specified in JIS K-6253 employing an A type durometer. The rubber hardness of elastomer 1 is preferably 15-70, and more preferably 20-60.

In the present invention, it is characterized that the static friction factor on the elastomer surface is not less than 0.2 and is not more than 0.9, and a range of 0.3-0.8 is more preferable. If the static friction factor is less than 0.2, an effect to rub the long-length film to correct wrinkles, distortions and strains is less, while, if 0.9 is exceeded, the long-length film to be rubbed is damaged, which is not preferable.

The static friction factor of the elastomer can be measured by the following method.

(Measurement of Static Friction Factor of Elastomer)

FIGS. 3(a), 3(b) and 3(C) show an example of a measuring method of the static friction factor of the elastomer relating to the present invention.

The friction factor of an object to be measured (formed object made of vulcanized rubber) was measured through a ball-penetrator (SUS, diameter of 6 mm) method by the use of HEIDON SURFACE NATURE TESTING MACHINE TYPE: HEIDON-14D (made by Shinto Scientific Co. Ltd.). FIG. 3(a) shows a diagram of principle of the present test.

In this HEIDON SURFACE NATURE TESTING MACHINE, a weight for vertical load is attached on a ball made of SUS through a supporting member as shown in FIG. 3(a), and this ball made of SUS is pressed on a test piece that is cut off from the elastomer by the force of the weight (200 g) for vertical load. Then, there is measured the frictional force generated when the test piece is moved toward the right side of FIG. 3(a) in the case of viewing the page vertically. FIG. 3(b) shows a tear-off test specimen and the measuring direction, and FIG. 3(c) shows a cross-sectional view of a test specimen and a tear-off section.

Other measuring conditions in the aforesaid testing machine are described below.

Measuring jig; Ball-penetrator (SUS, diameter of 6 mm)

Sample size; Sample size is not limited in particular, but a size capable of securing a travel distance of 50 mm or more is preferable.

Test load; 200 g (Weight for vertical load)

Test speed; 600 mm/min

Ambience; 23° C.±2, 50%±10 RH (No dew condensation within air-conditioning range is allowed)

Elastomer 1 relating to the present invention is preferably surface-modified rubber, and for securing the static friction factor within the aforesaid range for elastomer 1, it is preferable to use methods which have been disclosed such as a method described in Japanese Patent O.P.I. Publication No. 7-158632 to use a silicone rubber layer in which fluorine resin powder processed by sodium-naphthalene complex is filled, a method described in Japanese Patent O.P.I. Publication No. 9-85900 to use a thin film formed by melt of ultra-high molecular polyolephine powder, a method described in Japanese Patent O.P.I. Publication No. 11-166060 to form condensation polymer of hydrolysate of alkoxy silane on vulcanized rubber, a method described in Japanese Patent O.P.I. Publication No. 11-199691 to cause a monomer having a functioning group to conduct hot reaction with rubber, a method described in Japanese Patent O.P.I. Publication No. 2000-198864 to cause rubber to react on silica, a method described in Japanese Patent O.P.I. Publication No. 2002-371151 to cause fluoline-containing rubber and a monomer having a functioning group to conduct hot reaction and a method described in Japanese Patent O.P.I. Publication No. 2004-251373 to use chloroprene-based rubber. In the present invention, a method to use rubber for the elastomer and to conduct organic halogen compound treatment on the surface of the elastomer, for adjustment, as described in Japanese Patent O.P.I. Publication No. 2000-158842 is more preferable.

The rubber which can be denatured by organic halogen compound treatment includes acrylonitrile-butadiene rubber, chloroprene rubber, stylene-butadiene rubber, synthetic isoprene rubber, polybutadiene rubber, ethylene-propylene-dine ternary copolymer rubber, and natural rubber. Preferable elastomer for this object is acrylonitrile-butadiene rubber. These rubber are usually used after being vulcanized, and vulcanization used in this case is by an ordinary vulcanizing method used in the business field.

Examples of organic halogen compounds usable to modify the above rubber include halogenated succinimide like N- bromosuccinimide, a halogenated compound of isocyanuric acid like trichloroisocyanuric acid or dichloroisocyanuric acid, and halogenated hydantoin like dichlorodimethylhydantoin. Of these, the trichloroisocyanuric acid is preferable.

For making an organic halogen compound to work on the rubber surface, it is preferable to use it in appropriated concentration after dissolving it in an organic solvent. A solvent to be used for this purpose is requested not to react on an organic halogen compound, and an organic solvent which can be used includes, for example,

-   aromatic hydrocarbon such as benzene and xylene, ethers such as     diethyl ether, dioxane and tetrahydrofuran, esters such as ethyl     acetate, ketones such as methylethyl ketone and cycrohexanon and     chlorinated hydrocarbons such as ethyl chloride and chloroform.     Concentration of organic halogen compound in the organic solvent in     the case of treating the rubber surface is not limited in     particular, but it usually is 2-10% by weight, and 4-6% by weight is     preferable. When the concentration is higher than 2% by weight, an     efficiency for denaturing rubber is excellent, while, when it is     lower than 10% by weight, it is easy to coat on the rubber surface     evenly and effectively, and denaturing effect is sufficient and     rubber is not hardened.

For making a solution of organic halogen compound to work on rubber, it has only to make both of them contact each other, and a specific method is not necessary. For example, it is possible to coat on the surface of rubber by means of spray or a brush, or rubber may be immersed in a solution, or a solution of organic halogen compound can be put on rubber through rubbing.

A wrap angle of elastomer 1 to long-length film F is determined by arrangement of guide rollers 2 and 2′ which are arranged before and after elastomer 1. When rappu angle is set to be large, higher rubbing effect can be obtained because treating time for long-length film F to pass through elastomer 1 can be extended, and it is set to be less than 180° for transporting stably without causing wrinkles, scratches and meandering, and it is set preferably to be not less than 1° and to be less than 135°, and more preferably to be not less than 50 and to be less than 90°. It is also possible to extend treating time equally by enlarging a diameter of elastomer 1, and it is preferable that a diameter is less than 200 cm from the viewpoint of a space occupied and cost, and it preferably is not less than 5 cm and is less than 100 cm, further preferably is not less than 10 cm and is less than 50 cm.

The contact pressure applied on long-length film F on elastomer 1 can be controlled by the air pressure by air nozzle 5 stated above, and it is also determined by the tension and a roll diameter in the film transport system. It is preferable to control the tension in the transport system, because the roll diameter is also related to the aforesaid treating time. To obtain the effect of the present invention, it is preferable to keep the contact pressure to be high, but if it is established to be too high, a liquid film of the liquid is broken and elastomer 1 comes in contact with long-length film directly, resulting in scratches which are caused easily by rubbing. In general, 9.8×10² Pa or less is preferable, and a range of 5×10 Pa-9.8×10² Pa is more preferable, and the contact pressure is established more preferably to be in a range of 5×10 Pa-4.9×10² Pa.

From the viewpoint of preventing generation of a watermark, it is preferable to control a period of time during which the treated surface of the long-length film is moisturized by a liquid, by adjusting a distance between the elastomer and air nozzle 6, and a period of time during which the treated surface is moisturized is preferably in a range of 2-60 sec. In other words, a treating time between a starting point of moisturizing the treated surface with a device of moisturizing the treated surface and a termination point of removing the liquid with a device of removing the liquid is in a range of 2-60 sec. A starting point of the time during which the treated surface of the long-length film is moisturized, is a moment to start treating by elastomer 1 when a liquid supply device (for example, nozzle 8) for moisturizing the long-length film surface is not provided in advance, and the starting point is a moment when a liquid is jetted from the liquid supply device and thereby, the treated surface of the long-length film is moisturized, when a liquid supply device (for example, nozzle 8) is provided. A termination point of moisturizing time means a point of time when at least 95% of droplets sticking to the treated surface of the long-length film have scattered or evaporated. A temperature of air jetted from air nozzle 6 is preferably in a range of a room temperature—80° C., and it is more preferably in a range of 40-70° C.

FIGS. 6(a)-6(e) show pattern diagrams each showing an installation location of air nozzle 5 or 6 and the direction of air spewing. FIG. 6(a) shows that air is sprayed in the direction against the film traveling direction, while, FIGS. 6(b) and 6(c) show that air is sprayed toward the outside of the film. Each of FIGS. 6(d) and 6(e) shows an arrangement suitable for each of air nozzles 5 and 6 installed mainly on the opposite side of the treated surface of a film, and this arrangement is highly effective for preventing over-flow of liquid to a back side of the film.

In the present invention, it is preferable that rinse nozzle 12 that is identical to nozzle 8 and can jet a liquid is arranged at a position shown in each of FIGS. 4(a) and 4(b), on the side to be rubbed of the long-length film, so that cleaning by liquid may be added.

Rinse nozzle 12 is installed to be close to guide roller 2′, and jets a liquid on the surface of the long-length film F rubbed by elastomer 1. In this case, for a liquid to be jetted from rinse nozzle 12, an unused liquid supplied from another liquid reservoir tank is preferably used, or liquid obtained by cleaning liquid 4 reserved in liquid tank 3 is preferably used. In each of FIGS. 4(a) and 4(b), liquid tank 3 and rinse nozzle 12 are connected to each other through piping, and liquid 4 reserved in liquid tank 3 is drawn out by pressure pump 9 provided on the half way of the piping, and is supplied to rinse nozzle 12 after being cleaned by barrier filter 10, to be jetted. The surface rubbed by elastomer 1 of long-length film F is rinsed and cleaned by a liquid jetted from the rinse nozzle 12, whereby, foreign materials which are accompanied by a liquid to stick to elastomer 1 again are rinsed away. Incidentally, a liquid jetted from rinse nozzle 12 hits the film surface or the surface of elastomer 1, to fall by gravity to be collected in liquid tank 3. FIG. 4(c) shows an example wherein, after liquid 4 is jetted on the film surface by rinse nozzle 12, the film is bent in terms of its traveling direction by guide roller 2″, and air is jetted on the bent portion from air nozzle 6.

Further, though the barrier filter used in this case can be selected arbitrarily, a filter with a mesh in terms of a diameter of a hole of 0.1-10 μm is used independently or in combination arbitrarily. Further, a cartridge filter of a pleat-interfolded type can be selected advantageously on the points of a filtration life and easy handling.

A filtration and circulation flow rate needs to be established so that the number of foreign materials in the liquid tank may not be increased by foreign materials taken in from the film surface, with the passage of time. For the quantification of the number of foreign materials floating in a liquid, HIAC/ROYCO Liquid Fine Particle Counter Model 4100 manufactured by Nozaki & Co., Ltd. is used easily, and a fraction size of the filter and a circulation flow rate can be adjusted so that particles of the size to be removed may not increase.

As liquid 4, there is no limit in particular, and it is preferable to select the liquid that does not dissolve and extract a component contained in long-length film F or a subbing layer incorporated in the base surface through coating or other methods, and examples thereof include organic solvent such as methanol, ethanol, isopropyl alcohol, acetone, methyl acetate, toluene, and xylene, or a fluorine-based solvent, water or pure water containing acid, alkali, salt, surfactant and deformer, and most preferable is pure water.

In the present invention, a temperature of the aforesaid liquid 4 is usually 0-100° C., and a temperature ranging from 30° C. to 100° C. is especially preferable, and a temperature of the elastomer ranging from 30° C. to 100° C. simultaneously is preferable, for obtaining the effect of the present invention. Temperature adjustment of light 4 is preferably conducted through hot water circulation in a normal heater system, and a temperature of the elastomer is preferably adjusted by warming by immersing in hot water for appropriate time or by circulating hot water in the inside of the elastomer.

FIGS. 5(a)-5(d) show a cleaning method for elastomer 1 relating to the present invention.

FIG. 5(a) shows a method of using an ultrasonic transducer, FIG. 5(b) shows a method of using a blade and FIG. 5(c) shows a method to rub with another elastomer such as a rubber roller. FIG. 5(d) is also one showing an installation position of air nozzle 8, and any position of 8 a, 8 b, 8 c, 8 d and 8 e can be used-for installation.

In FIG. 5(a), symbol 13 represents an ultrasonic transducer. This ultrasonic transducer 13 emits ultrasonic waves on the surface of elastomer 1 to let foreign materials transferred thereon fall off. Meanwhile, for transmitting the emitted ultrasonic waves to the surfaces of elastomer 1, ultrasonic transducer 13 is arranged so that liquid 4 may be held between itself and elastomer 1. Further, it is also possible to provide a plurality of transducers, and in this case, it is necessary to determine intervals between the ultrasonic transducers so that overlapping of ultrasonic waves coming from adjoining transducers may be uniform.

As a frequency of ultrasonic transducer 13, it is possible to use a range of 10-100000 kHz. Further, it is also possible to combine plural transducers each oscillating a different frequency, or to use a transducer whose frequency can be modulated.

As an ultrasonic wave output per unit area of the transducer, it is possible to use a range of 0.1-2 W/cm². A distance from ultrasonic transducer 13 to long-length film F has its optimum point because of a standing wave, and it is preferable that the distance is made to be an integer multiple of the following expression; λ=C/f where, λ represents a wavelength, C represents ultrasonic wave transmission wave in a liquid and f represents a frequency.

Ultrasonic wave treatment is preferably conducted within a time range of 1-100 sec and within a frequency range of 10-100000 kHz. A range of 40-1500 kHz is preferable in particular.

Ultrasonic transducer to be used includes WS-600-28N, WS-600-40N, WS-600-75N, WS-600-100N, WS-1200-28N, WS-1200-40N, WS-1200-75N, WS-1200-100N, N60R-M, N30R-M, N60R-M, W-100-HFMKKIIN and W-200-HFMKIIN, produced by Honda Electronics Co. Ltd., and some other products, produced by Alex Corporation.

Blade 14 shown in FIG. 5(b) is made of materials such as rubber, sponge and brush which do not damage a surface of the elastomer, and it scrapes off foreign materials sticking to a surface of the elastomer.

In FIG. 5(c), foreign materials sticking to a surface of the elastomer can be removed by roller 15 that is made of materials lower than elastomer 1 in terms of hardness which do not damage a surface of the elastomer such as rubber, sponge, brush or a non-woven fabric, and rubs continuously a surface of the elastomer.

In the present invention, for correcting more accurately wrinkles, distortions and strains, and a device to prevent meandering of a long-length film is preferably added, and it is preferable that a meandering correction device such as an edge position controller (which is sometimes called EPC) described in Japanese Patent O.P.I. Publication No. 6-8663, or a center position controller (which is sometimes called CPC) is used. Each of these devices is one that detects film edges by an air servo sensor or by a photosensor, then, controls the film transporting direction based on information of the detection and thereby tries to keep the edge of the film and the center in a width of the film at their fixed positions. As an actuator for the means, one or two guide rolls or flat expander rolls with drive are swung from side to side (or upward and downward) for the line direction specifically, to correct meandering, or, small-sized two pinch rolls constituting one set are arranged on the right and left sides of the film (one roll is arranged on each of the obverse side and the backside of the film, and the foregoing is arranged on each of both sides of the film) to pinch and pull the film and thereby to correct meandering (cross guider system). With respect to a principle of correction of meandering in the aforesaid devices, when the film is compelled to travel to the left side while the film is running, the former system employs a method to tilt the roll so that the film may travel to the right side and in the latter method, one set of pinch rolls on the right side are nipped to pull the film to the right side.

It is preferable that the meandering prevention device is installed within a range of 2-30 m in the upstream side or downstream side from a starting point of the position where the elastomer relating to the present invention is arranged, and it is more preferable that at least one device is installed in each of the upstream side and the downstream side.

An optical film relating to the present invention is characterized to be obtained through the aforesaid manufacturing method, and it is preferable that the optical film is an anti-reflection film.

The anti-reflection film in the present invention is characterized to be a laminated body of optical interference layers in which a high refractive layer and a low refractive layer are laminated in this order from the support side on at least one surface of the support (according to circumstances, other layers are added). A hard coat layer is preferably provided between a support and the anti-reflection layer. The hard coat layer is provided by the use of active light curing resin which will be explained later.

With respect to the anti-reflection layer, it is preferable that an optical layer thickness of a high refractive layer and that of a low refractive layer are set to λ/4, for light having a wavelength of λ. The optical layer thickness means a quantity defined by the product of refraction n of the layer and the layer thickness d. The extent of refractive index is mostly determined by metal or compound contained, and for example, Ti makes it. high, Si makes it low, and a compound containing F makes it further lower, thus, the refractive index is established by the combination. The refractive index and the layer thickness are computed and calculated through measurement of spectral refraction factor.

In this case, when obtaining a layer by coating a solution containing metal compound on a support, this anti-reflection optical characteristic is determined by the physical layer thickness alone as stated above.

A color of the reflected light in the vicinity of 550 nm, in particular, changes between reddish-purple and bluish-purple, when the layer thickness is changed by an amount as small as several μm. This color shading is hardly visible when an amount of transmitted light coming from a display is large, but the color shading is highly visible when the amount of light is small, or when a display is turned off, resulting in deteriorated visibility. Further, when a slippage of the layer thickness is great, it is impossible to lower the reflection coefficient at 400-700 nm, and it becomes difficult to obtain desired anti-reflection characteristics.

A long-length film used in the present invention is not particularly limited, but provided, for example, are a polyester film, a cellulose ester film, a plycarbonate film, a ployethersulfone film and a cyclic olefin resin film. Those prepared by a melt-cast method or a solvent-cast method are preferably employed. Of these, a cellulose ester film is preferable in the present invention. A cellulose ester film oriented in at least one direction is particularly preferable.

For example, preferably employed as the cellulose ester film are Konica Minolta Tac KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC8UE, KC4UE and KC4FR (all produced by Konica Minolta Opt, Inc.). The thickness of a long-length film is 10-500 μm, and preferably 10-200 μm. The length of a long-length film is 100-10000 m, and preferably 300-5000 m. It is also preferable that the usable width is 1-4 m.

As the raw material of cellulose for the cellulose ester to be employed in the present invention, cotton linter, wood pulp and kenaf can be cited though the material is not specifically limited. These raw materials may be used in combination with an optional mixing ratio, and cotton linter having at least 50% by weight is preferably employed.

Regarding the cellulose ester, the reaction is carried out using an organic acid such as acetic acid, an organic solvent such as methylene chloride and a proton catalyst such as sulfuric acid when the acylating agent for the cellulose of raw material is an acid anhydride such as acetic anhydride, propionic anhydride and butylic anhydride. The reaction is carried out using a basic compound such as an amine as a catalyst when the acylating agent is an acid chloride such as CH₃COCl, C₂H₅COCl and C₃H₇COCl. In concrete, the cellulose ester can be synthesized referring the method described in Japanese Patent O.P.I. Publication No. 10-45804. In the case of the cellulose ester, an acyl group reacts to a hydroxy group in a cellulose molecule. The cellulose molecule is composed of a number of linked glucose units, and the glucose unit contains 3 hydroxyl groups. The number of acyl groups induced by these 3 hydroxyl groups is designated as a substitution group.

In the case of cellulose triacetate, an acetyl group is bonded to all 3 hydroxyl groups in a glucose unit.

Cellulose ester usable for a cellulose ester film is not particularly limited, but it is preferable that the substitution degree of total acyl groups is 2.40-2.98, and it is more preferred that the substitution degree of an acetyl group is at least 1.4.

The substitution degree of an acyl group can be measured according to a method specified in ASTM-D817-96.

Preferable examples of cellulose ester include cellulose acetate such as cellulose triacetate or cellulose diacetate, and cellulose ester such as cellulose acetate propionate cellulose acetate butyrate or cellulose acetate propionate butyrate, in which an acetyl group, a propionate group or a butyrate group is bonded. In addition, butyrate includes n- as well as iso-. Cellulose acetate propionate having a large substituting degree of a propionate group exhibits excellent water resistance.

It is preferable that cellulose ester having a number average molecular weight Mn of 70000-250000 (a measurement method described below) exhibits enhanced mechanical strength of the resulting film, and appropriate dope viscosity. More preferably employed is cellulose ester having a number average molecular weight Mn of 80000-150000. Cellulose ester having a ratio of weight average molecular weight Mw to number average molecular weight Mn (Mw/Mn) of 1.0-5.0 is preferably used, and of 1.5-4.5 is more preferably used.

<<Measurement of the Number Average Molecular Weight of Cellulose Ester>>

The number average molecular weight of cellulose ester is determined via high speed liquid chromatography under the conditions described below.

Solvent: acetone

Column: MPWx1 (manufactured by TOSOH Corp.)

Sample concentration: 0.2 weight/volume %

Flow rate: 1.0 ml/minute

Sample injection volume: 300 μl

Standard sample: methyl polymethacrylate (Mw=188200)

Temperature: 23° C.

It is preferable that an amount of metal employed during manufacturing cellulose ester or that of metal contained in cellulose ester, which is slightly mixed in utilized materials is minimized. The total content of metals such as Ca, Mg, Fe and Na is preferably at most 100 ppm.

[organic Solvent]

Methylene chloride which is a chlorine based organic solvent may be provided as a cellulose ester solution employed for dissolution of cellulose ester, or an organic solvent usable for preparation of a dope. Listed as a non-chlorine based organic solvent may be methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolan, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, or nitroethane.

When these organic solvents are used for dissolving cellulose triacetate, various dissolving methods such as a high temperature dissolution method, a cooling dissolution method and a high pressure dissolution method are preferably applied by which insoluble substance can be reduced, while the dissolution method at room temperature is also applicable.

Methyl acetate, ethyl acetate and acetone are preferably employed without using methylene chloride for cellulose esters other than the cellulose triacetate, although methylene chloride is also usable. Of these, methyl acetate is specifically preferable. In the present invention, the solvents having high dissolving ability to the above cellulose esters are referred to as good solvent, and the solvent exhibiting high dissolving effect and used in major amount is referred to as a principal (organic) solvent.

The dope preferably contains an alcohol having 1 to 4 carbon atoms in an amount of 1 to 40% by weight additionally to the foregoing organic solvent. The alcohols are used as a gelling agent by which the web is gelled and strengthen when the dope is cast on a metal support and the alcohol content is increased due to the evaporation of other solvent. As a result of that the web can be easily peeled off from the metal support. The alcohol also plays a role of accelerating dissolution of the cellulose ester in the non-chlorine organic solvent when the alcohol content is low.

Examples of the alcohols having 1 to 4 carbon atoms include, methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol and tert-butanol.

Among them, ethanol is preferable, which exhibits excellent properties such as dope stability, a low boiling point, drying ability and no toxicity. These organic solvents are designated as poor solvent, because they each have a low dissolving ability with respect to the cellulose ester.

[Preparation of a Cellulose Ester Film with a Solution-casting Film Formation Method]

A film formation method of a cellulose ester film employed as a support will be described. The cellulose ester film is prepared with a solution-casting film formation method.

1) Dissolution Step

The dissolution step is one in which cellulose ester (in the flake form), a polymer or additives are dissolved, while stirring, in organic solvents mainly comprised of good solvents for the cellulose ester, employing a dissolution vessel, or a polymer solution or an additive solution is added to a cellulose ester solution, whereby a dope is prepared. In order to carry out dissolution of cellulose ester, there are various methods such as a method in which dissolution is carried out at a normal atmospheric pressure, a method in which dissolution is carried out at a temperature lower than the boiling point of the main solvent, a method in which dissolution is carried out at a temperature higher than the boiling point of the main solvent under an increase of pressure, a cooling dissolution method disclosed in Japanese Patent O.P.I. Publication Nos. 9-95544, 9-95557, and 9-95538, and a method in which dissolution is carried out at a high pressure disclosed in Japanese Patent O.P.I. Publication No. 11-21379. The method is especially preferred in which dissolution is carried out at a temperature higher than the boiling point of the main solvent under an increase of pressure.

The cellulose ester concentration of the dope is preferably 10-35% by weight. The resultant dope is filtered employing filter materials, is then defoamed, and is subsequently pumped to the next process.

2) Casting Step

The casting step is one in which a dope is conveyed to a pressure die through a pump (for example, a pressure type metering gear pump), and cast from said pressure die onto a casting site of a moving endless metal belt such as a stainless steel belt or a metal support such as a rotating metal drum. The pressure die is preferred in which the slit shape at the mouth piece portion can be regulated and the layer thickness is readily controlled to be uniform. The pressure die is a coat hunger die or a T die, but either one is preferably employed. The surface of the metal support for casting is specular. In order to increase the casting speed, two or more pressure dies may be provided on the metal support and dopes divided into two or more may be simultaneously cast on the metal support.

3) Solvent Evaporation Step

The solvent evaporation step is one in which a web is heated on a metal support and solvents are evaporated till the web is capable of being peeled from the metal support (A dope film is called a web after casting the dope on a metal support). In order to evaporate solvents, methods include a method in which air is blown from the web side, and/or a method in which heating is carried out from the reverse surface of the support employing liquid, and a method in which heating is carried out from the surface as well as the revere surface employing heat radiation. Of these, the reverse surface liquid heating method is preferred due to high drying efficiency. Further, these methods are preferably combined. It is preferred in the reverse surface liquid heating method that heating is carried out at a temperature not more than the boiling point of the main solvent or a solvent having the lowest boiling point of solvents used.

4) Peeling Step

The peeling step is one in which a web, which has been subjected to evaporation of solvents on the support, is peeled at the peeling site. The peeled web is conveyed to the subsequent step. When the residual solvent amount is too excessive, it may be difficult to peel the web. On the contrary, when peeling is carried out after fully drying the web on the support, a part of the web may peel prior to the peeling site.

Provided as a method to increase the film forming speed is a gel casting method (in which peeling can be carried out even though the amount of residual solvents is relatively large).

The cellulose ester films are used as supports employing the solution-casting film formation method with no limitation to be used while referring generally to methods described, for example, in U.S. Pat. Nos. 2,492,978, 2,739,070, 2,739,069, 2,492,977, 2,336,310, 2,367,603, and 2,607,704; British Patent Nos. 64,071 and 735,892; and Japanese Patent Examined Publication Nos. 45-9074, 49-4554, 49-5614, 60-27562, 61-39890, and 62-4208.

Solvents employed to prepare a dope of cellulose ester in the solution-casting film formation method may be used singly or in combination with at least two kinds. However, in view of enhancing production efficiency, it is preferable that good and poor cellulose ester solvents are mixed and then employed. Further, it is preferable to increase the amount of good solvents since solubility of cellulose esters is enhanced. The mixing ratio of good solvent to poor solvent is preferably within the range of 70-98% by weight of good solvent and of 2-30% by weight of poor solvent.

Good solvents are defined as those which individually dissolve cellulose esters, while poor solvents are defined as those which individually swell cellulose esters but do not dissolve them. Thus, a good solvent or a poor solvent is changed as an objective depending on an average acetylation degree. When acetone, for example, is used as a solvent, it becomes a good solvent in the case of cellulose ester having an amount of bonded acetic acid of 55% and a poor solvent in the case of cellulose ester having an amount of bonded acetic acid of 60%.

Good solvents employed in the present invention are not particularly limited. In the case of cellulose triacetates, examples include organic halogen compounds such as methylene chloride, dioxolans and methyl acetate while in the case of cellulose acetate propionate, examples include methylene chloride, acetone, and methyl acetate.

Further, poor solvents usable in the present invention are also not particularly limited, and for example, preferably employed are methanol, ethanol, i-propyl alcohol, n-butanol, cyclohexane, acetone, and cyclohexanone.

When the above dope is prepared, a conventional method can be utilized as a dissolution method of cellulose ester, but a method is more preferred in which while stirring, dissolution is performed under pressure application while heating within the range which is at least at the boiling point of solvents used at normal pressure and in which solvents do not boil, due to prevention of formation of lump-shaped insoluble substances called “gel” or “mamako”.

A method is also preferably employed in which after wetting or swelling cellulose ester upon being blended with poor solvents, dissolution is performed by blending with good solvents.

Types of pressure vessels are not particularly limited as long as they can function at the specified pressure, and can perform stirring and heating under the pressure. Other than that, the pressure vessel is appropriately fitted with measuring instruments such as a manometer and a thermometer. Pressure may be applied employing a method in which inert gasses such as nitrogen gas are subjected to press fitting or via an increase in vapor pressure of solvents due to heating. It is preferable that from the exterior, heating is performed, for example, a jacket type vessel is preferred since the temperature is easily controlled.

Heating temperature after the addition of a solvent is preferably higher than the boiling point of the added solvent, and a temperature lower than the boiling point of the solvent is preferable in view of solubility of cellulose ester, but when the heating temperature is excessively high, the desired pressure also becomes relatively high, resulting in degradation of productivity. Heating temperature is preferably in the range of 45-120° C., is more preferably in the range of 60-110° C., but is most preferably in the range of 70-105° C. Further, the pressure is controlled so that solvents do not boil at the specified temperature.

Other than cellulose ester and solvents, additives such as necessary plasticizers or UV absorbents are mixed to the solvents in advance, and dissolved or dispersed. The resulting solution or dispersion may be charged into solvents prior to dissolution of cellulose ester, or charged into a dope after dissolution of cellulose ester.

Cellulose ester is dissolved and removed from the vessel while cooling, or drawn from the vessel employing a pump, and then cooled employing a heat exchanger. Thereafter, this is fed for preparing films. During this operation, the cooling temperature may reach room temperature, but it is preferred that casting is conducted under the condition at 5-10° C. lower temperature via cooling than the boiling point to reduce a dope viscosity.

The substitution degree of an acyl group is determined according to a method specified in ASTM-D 817-96.

The cellulose ester is produced generally by a method called “solution-casting film formation method” as described later. A dope (a cellulose ester solution) is cast from a pressure die onto a metal support such as an endless metal belt running endlessly (a stainless bett, for example) or a rotating metal drum (a cast iron drum with the chromeplated surface) via this method, and a web on the casting metal support (also referred to simply as a metal support) is peeled off to be produced after drying.

When a cellulose ester film is used as a liquid crystal display employed outdoors in view of minimizing degradation of properties, it is preferable that the following UV absorbents are incorporated.

Preferably employed as UV absorbents may be those which exhibit sufficient absorption of ultraviolet rays at a wavelength of at most 370 nm and minimal absorption of visible light at a wavelength of at least 400 nm. Examples of the UV absorbents include an oxybenzophenone based compound, a benzotriazole based compound, a salicylic acid ester based compound, a benzophenone based compound, a cyanoacrylate based compound and a nickel complex salt based compound, but the present invention is not limited thereto.

In the present invention, a cellulose ester film having a thickness of 10-200 μm is preferably employed as a long-length film, but a cellulose ester film having a thickness of 30-70μm is more preferable. Though coating unevenness has easily appeared previously in the case of using such the film thickness, stable coatability is possible to be accomplished even in a thin film having a thickness of at most 70 μm.

When an optical film is provided on the above-described support in the present invention, the optical film is provided in such a way that the film thickness deviation with respect to the average film thickness is ±8%, preferably within ±5%, and more preferably within ±1%. The remarkable effect is produced when the manufacturing method of the present invention is applied to optical film having a wide width of a least 1400 mm. The upper limit of the width of an optical film preferably utilized is not particularly limited from the aspect of accuracy of film thickness, but at most 4000 mm is preferable in view of production cost.

Regarding the optical film of the present invention, transportation and winding processes can be easily conducted by containing a matting agent in a cellulose ester film.

The particle of the matting agent is preferably as small as possible. Examples of the particle include an inorganic particle of silicone dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talk, baked calcium silicate, hydrated calcium carbonate, aluminum silicate or magnesium silicate; and polymethacrylic acid methylacrylate resin powder, acrylstyrene based resin powder, polymethymethacrylate resin powder, silicon based resin powder, polystyrene based resin powder, polycarbonate resin powder, benzoguanamine based resin powder, melamine based resin powder, polyolefin based resin powder, polyester based resin powder, polyamide based resin powder, polyimide based resin powder, or polyethylene fluoride based resin powder, but crosslinked polymer particles are particularly preferable. The present invention is not limited thereto.

Of these, silicone dioxide is preferable to control the dynamic friction factor, and it is also preferable to reduce haze of the film. The average particle diameter of the primary particles or the secondary particles is preferably 0.01-5.0 μm, and the content of the particles is preferably 0.005-0.5% by weight, based on cellulose ester.

Particles such as silicone dioxide and the like are often surface treated employing an organic compound, and these are preferable since haze of the film can be reduced.

As preferable organic compound for surface treatment, a halosilane compound, an alkoxysilane compound, a silazane compound and a siloxane compound are cited. Particles having a large average particle diameter exhibit large slipping effect, whereas particles having a small average particle diameter exhibit excellent transparency. Thus, the average particle diameter of the primary particles is preferably at most 20 nm, more preferably 5-16 nm, and still more preferably 5-12 nm.

Regarding these particles, it is preferable that a roughened structure of 0.01-1.0 μm is formed on the cellulose ester surface.

As the silicone dioxide particle, Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, and TT600, each produced by Nihon Aerosil Co., Ltd., are usable. Aerosil 200V, R972, R972V, R974, R202 and R812 are preferable. These particles are used in combination with at least two kinds. In the case of using these particles in combination with at least two kinds, the admixture in an arbitrary ratio is usable. In such the case, particles having a different average particle diameter or particles made of a different material, Aerosil 200V and R972, for example, are usable in a weight ratio of from 0.1:99.9 to 99.9:0.1. A commercially available product such as Aerosil R976 or R811, produced by Nihon Aerosil Co., Ltd. is also usable.

Examples of commercially available silicone resins include TOSPERL 103, 105, 108, 120, 145, 3120 and 240, manufactured by Toshiba Silicone Co., Ltd.

In order to measure a primary average particle diameter utilized in the present invention, the particles were observed employing a transmission electron microscope (at a magnification of 500,000-2,000,000 times) to determine the primary average particle diameter as an average value via observation of 100 particles.

The apparent specific gravity of particles is preferably at least 70 g/liter, more preferably 90-200 g/liter and specifically preferably 100-200 g/liter. The larger is the apparent specific gravity, dispersion having the higher concentration can be prepared, which is preferable because of improved haze and less aggregation, and is specifically preferable during preparation of a dope having a high solid density.

Silicon dioxide particles having a primary particle diameter of not more than 20 nm and an apparent specific gravity of 70 g/liter can be prepared, for example, by combustion of a mixture of gaseous silicon tetrachloride and hydrogen in air at 1000-1200° C. The above-described apparent specific gravity is determined by sampling a predetermined volume of silicon dioxide particles in a messcylinder to measure the weight and is calculated according to the following equation.

Apparent specific gravity (g/liter)=weight of silicon dioxide (g)/volume of silicon dioxide (liter)

A preparation method of a dispersion of particles utilized in the present invention includes, such as the following three types.

<Preparation Method A>

Dispersion is performed by use of a homogenizer after a solvent and particles have been stirring mixed. This is designated as particle dispersion. The particle dispersion is added into a dope solution to be mixed.

<Preparation Method B>

Dispersion is performed by using a homogenizer after an organic solvent and particles have been mixed while stirring. This is designated as a particle dispersion. Separately, a small amount of cellulose ester is added into an organic solvent and is dissolved while stirring. The aforesaid particle dispersion is added therein and the resulting solution is mixed. This is designated as a particle additive solution, and the particle additive solution is sufficiently mixed with a dope employing an in-line mixer.

<Preparation Method C>

A small amount of cellulose ester is added into an organic solvent and is dissolved while stirring. Particles are added therein and dispersed by using a homogenizer. This is designated as a particle additive solution. The particle additive solution is sufficiently mixed with a dope employing an in-line mixer.

Preparation method A is superior in dispersibility of silicon dioxide particles and preparation method C is superior in that silicon dioxide particles are hard to be re-aggregated. Among them, the above-described preparation method B is a preferable method which is superior in both of dispersibility of silicon dioxide particles and re-aggregation resistance of silicon dioxide particles.

<Dispersion Methods>

The concentration of silicon dioxide at the time of dispersing silicon dioxide particles by being mixed with a solvent is preferably 5-30% by weight, more preferably 10-25% by weight and most preferably 15-20% by weight.

The addition amount of silicon dioxide particles against cellulose ester is preferably 0.01-5.0 parts by weight, more preferably 0.05-0.2 parts by weight and most preferably 0.08-0.12 parts by weight. The larger addition amount is, the superior dynamic friction factor of a cellulose ester film, while the smaller addition amount is, the lower haze and the less aggregation.

Organic solvents utilized as a dispersion include preferably lower alcohols such as methanol, ethanol, propyl alcohol, isopropyl alcohol and buthanol. Organic solvents other than lower alcohols are not specifically limited, but preferably utilized are organic solvents which are employed at the time of preparing a dope.

As a homogenizer, an ordinary homogenizer can be utilized. Homogenizers can be roughly classified into a media homogenizer and a media-less homogenizer. For dispersion of silicon dioxide particles, a media-less homogenizer is preferred due to a lower haze. A media homogenizer includes such as a ball mill, a sand mill and a die mill. A media-less homogenizer includes an ultrasonic type, a centrifugal type and a high pressure type, however, a high pressure homogenizer is preferable in the present invention. A high pressure homogenizer is an apparatus to make a special condition such as a high share or high pressure state by passing a composition, comprising particles and a solvent having been mixed, through a fine tube at a high speed. In the case of processing by a high pressure homogenizer, it is preferable, for example, to set the maximum pressure condition in a fine tube having a diameter of 1-2000 μm of at least 9.8 MPa and more preferably of at least 19.6 MPa. Further, at that time, preferable are those in which the maximum speed of at least 100 m/sec and the heat transmission rate of at least 420 kJ/hour.

High pressure homogenizers such as described above include a high pressure homogenizer (product name : Microfluidizer) manufactured by Microfluidics Corporation or Nanomizer manufactured by Nanomizer Corp., in addition to Manton-Gaulin type high pressure homogenizers such as a homogenizer manufactured by Izumi Food Machinery Co., Ltd. and UHN-01 manufactured by Sanwa Machine Co., Inc.

It is preferable that during containing the above particles, they are evenly distributed in the cellulose ester film thickness direction, but they are preferably distributed so as to be present adjacent mainly to the surface. For example, it is preferable that at least two kinds of dopes are simultaneously cast from a die with a co-casting method to place the dope containing particles on the surface layer side. In this way, haze can be reduced, and dynamic friction factor can be lowered. Further, it is preferred that the dope containing particles in one layer on the surface layer side or both layers is placed by using 3 kinds of dopes.

A back coat layer containing particles can be provided on the back surface side to control a dynamic friction factor of a support. The dynamic friction factor can be controlled with size of added particles, an addition amount and a material.

Phosphate ester plasticizers and non-phosphate ester plasticizers are preferably usable as plasticizers employed in the present invention.

Examples of phosphate ester plasticizers include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate and tributyl phosphate.

Examples of non-phosphate ester plasticizers include phthalic acid ester, polyhydric alcohol ester, polycarboxylic acid ester, citric acid ester, glycolic acid ester, aliphatic acid ester, pyromellitic acid ester, trimellitic acid ester and polyester.

Of these, polyhydric alcohol ester, phthalic acid ester, citric acid ester, aliphatic acid ester, glycolic acid ester and polyester are preferable.

A polyhydric alcohol ester plasticizer is a plasticizer containing an ester of an aliphatic polyhydric alcohol having at least divalence and monocarboxylic acid, and it preferably contains an aromatic ring or a cycloalkyl ring in a molecule. It is preferably an aliphatic polyhydric alcohol ester having valence of 2-20.

The polyhydric alcohol usable in the present invention is expressed by following Formula (I). R₁—(OH)n  Formula (I) wherein, R₁ represents an organic group having a valence of n, n represents a positive integer of at least two, and an OH group represents an alcoholic or a phenolic hydroxyl group.

Examples of preferable polyhydric alcohol include: adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1.4-butanediol, dibutylene glycol, 1,2,4-bunanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane and xylitol, but the invention is not limited thereto. Specifically, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylol propane and xylitol are preferable.

As the monocarboxylic acid to be used in the polyhydric alcohol ester, a known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid and aromatic monocarboxylic acid may be employed, though the monocarboxylic acid is not specifically limited. Specifically, aliphatic monocarboxylic acid and aromatic monocarboxylic acid are preferable, since moisture permeability and storage ability are improved.

Examples of the preferable monocarboxylic acid are listed below but the present invention is not limited thereto.

A straight or branched chain carboxylic acid having 1 to 32 carbon atoms is preferably employed. The number of carbon atoms is more preferably 1-20, and specifically preferably 1-10. The addition of acetic acid is preferable for raising the compatibility with a cellulose ester, and the mixing of acetic acid with another carboxylic acid is also preferable.

As the preferable aliphatic monocarboxylic acid, saturated aliphatic acids such as acetic acid, propionic acid, butylic acid, valeric acid, caproic acid, enantic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexane acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanic acid, arachic acid, behenic acid, lignocelic acid, cerotic acid, heptacosanic acid, montanic acid, melisic acid and lacceric acid; and unsaturated aliphatic acids such as undecylenic acid, oleic acid, sorbic acid, linolic acid, linolenic acid and arachidonic acid can be exemplified.

Examples of preferable alicyclic carboxylic acid include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid and derivatives thereof.

Examples of preferable aromatic carboxylic acid include ones formed by introducing an alkyl group into the benzene ring of benzoic acid such as benzoic acid and toluic acid; and an aromatic monocarboxylic acid having two or more benzene rings such as biphenylcarboxylic acid, naphthalene carboxylic acid and tetralin carboxylic acid, and derivatives thereof, of these, benzoic acid is specifically preferable.

The molecular weight of the polyhydric alcohol ester is preferably 300-1500, and more preferably 350-750, though the molecular weight is not specifically limited. Larger molecular weight is preferable for storage ability, while smaller molecular weight is preferable for compatibility with cellulose ester.

The carboxylic acid to be employed in the polyhydric alcohol ester may be one kind or a mixture of two or more kinds of them. The OH groups in the polyhydric alcohol may be fully esterified or a part of OH groups may be left unreacted. Specific examples of the polyhydric alcohol ester are listed below.

Glycolate plasticizers are not limited, but alkylphthalylalkyl glycolates are preferably used. Examples of alkylphthalylalkyl glycolates include: methylphthalylmethyl glycolate, ethylphthalylethyl glycolate, propylphthalylpropyl glycolate, butylphthalylbutyl glycolate, octylphthalyloctyl glycolate, methylphthalylethyl glycolate, ethylphthalylmethyl glycolate, ethylphthalylpropyl glycolate, methylphthalylbutyl glycolate, ethylphthalylbutyl glycolate, butylphthalylmethyl glycolate, butylphthalylethyl glycolate, propylphthalylbutyl glycolate, butylphthalylpropyl glycolate, methylphthalyloctyl glycolate, ethylphthalyloctyl glycolate, octylphthalylmethyl glycolate and octylphthalylethyl glycolate.

Examples of phthalate plasticizers include: diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate and dicyclohexyl terephthalate.

Examples of citrate plasticizers include: acetyltrimethyl citrate, acetyltriethyl citrate and acetyltributyl citrate.

Examples of aliphatic acid ester plasticizers include: butyl oleate, methylacetyl ricinoleate and dibutyl sebacate.

A polyester plasticizer having a cycloalkyl group in the molecule thereof is preferably employed. For example, aromatic terminal type polyester plasticizers represented by following Formula (2) are preferable though the polyester plasticizer is not specifically limited. B-(G-A)_(n)-G-B  Formula (2)

In the above formula, B is a benzene monocarboxylic acid residue, G is an alkylene glycol residue having 2-12 carbon atoms, an aryl glycol residue having 6-12 carbon atoms or an oxyalkylene glycol residue having 4-12 carbon atoms, A is an alkylenecarboxylic acid residue having 4-12 carbon atoms or an aryldicarboxylic acid residue having 6-12 carbon atoms, and n is an integer of 1 or more. The polyester type plasticizer is constituted by the benzene monocarboxylic acid residue represented by B, the alkylene glycol residue, the aryl glycol residue or the oxyalkylene glycol residue represented by G, and an alkylenecarboxylic acid residue or an aryldicarboxylic acid residue represented by A; the plasticizer can be obtained by a reaction similar to that for obtaining usual polyester plasticizer.

As the benzene monocarboxylic acid component of the polyester type plasticizer employed in the present invention, for example, benzoic acid, p-tert-butylbenzoic acid, o-toluic acid, m-toluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, n-propylbenzoic acid, aminobenzoic acid and acetoxybenzoic acid are applicable. They can be employed solely or in combination.

Examples of the alkylene glycol with 2-12 carbon atoms as the component of the polyester type plasticizer include ethylene glycol, 1,2 propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol and 1,12-octadecanediol. These glycols are employed solely or in mixture of two or more kinds thereof. An alkylene glycol with 2-12 carbon atoms is particularly preferable since compatibility with cellulose ester is excellent.

Examples of the oxyalkylene glycol component with 4-12 carbon atoms forming the aromatic terminal type ester structure include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol and tripropylene glycol. These glycols can be employed singly or in combination of two or more kinds.

Examples of the alkylenedicarboxylic acid component with 4-12 carbon atoms forming the aromatic terminal type ester structure include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid and dodecanedicarboxylic acid. These acids can be employed solely or in a combination of two or more kinds. The examples of the arylenedicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, tetraphthalic acid, 1,5-naphthalenedicarboxylic acid and 1,4-naphthalenedicarboxylic acid.

The suitable number average molecular weight of the polyester type plasticizer to be employed in the present invention is preferably 300-1500, and more preferably 400-1000. The acid value and the hydroxyl group value are at most 0.5 mg KOH/g and at most 25 mg KOH/g, respectively, and preferably at most 0.3 mg KOH/g and 15 mg KOH/g, respectively. Synthesized examples of the aromatic terminal type ester plasticizer are described below.

<Sample No. 1 (Sample of Aromatic Terminal Type Ester)>

In a reaction vessel, 410 parts of phthalic acid, 610 parts of benzoic acid, 737 parts of dipropylene glycol, 365 parts of adipic acid and 0.40 parts of tetraisopropyl titanate as a catalyst were charged at once and stirred in nitrogen gas stream, and heated at a temperature of 130-250° C. until the acid value becomes at most 2 while formed water was continuously removed and excessive monohydric alcohol was refluxed by a reflux condenser. After that, distillate was removed under a reduced pressure of at most 1×10⁴ Pa, finally at most 4×10² Pa at a temperature of 200-230° C., and then the content of the vessel was filtered to obtain an aromatic terminal type ester plasticizer having the following properties.

-   Viscosity (mPa·s at 25° C.): 43400 -   Acid value: 0.2     <Sample No. 2 (Sample of Aromatic Terminal Type Ester)>

An aromatic terminal type ester having the following properties was obtained similarly to Sample 1, except that 410 parts of phthalic acid, 610 parts of benzoic acid, 341 parts of ethylene glycol and 0.35 parts of tetraisopropyl titanate as a catalyst were employed.

-   Viscosity (mPa·s at 25° C.): 31000 -   Acid value: 0.1     Sample No. 3 (Sample of Aromatic Terminal Type Ester)

An aromatic terminal type ester having the following properties was obtained similarly to Sample 1, except that 410 parts of phthalic acid, 610 parts of benzoic acid, 410 parts of 1,2-propylene diol and 0.35 parts of tetraisopropyl titanate as a catalyst were employed.

-   Viscosity (mpa·s at 25° C.): 38000 -   Acid value: 0.05     Sample No. 4 (Sample of Aromatic Terminal Type Ester)

An aromatic terminal type ester having the following properties was obtained similarly to Sample 1, except that 410 parts of phthalic acid, 610 parts of benzoic acid, 418 parts of 1,3-propylene diol and 0.35 parts of tetraisopropyl titanate as a catalyst were employed.

-   Viscosity (mpa·s at 25° C.): 37000 -   Acid value: 0.05

Specific compounds of the aromatic terminal ester type plasticizer are listed below, but the present invention is not limited thereto.

These plasticizers can be mixed and used singly or in combination with at least two kinds. In the case of a consumption amount of the plasticizer of less than 1% by weight with respect to cellulose ester, this is not desired because of not much effect to reduce moisture permeability of a film. In the case of c exceeding 20% by weight, this is also not desired since the plasticizer breeds out from a film, whereby the film characteristics are degraded. As a result, a consumption amount of the plasticizer is preferably 1-20% by weight, more preferably 6-16% by weight, and most preferably 8-13% by weight.

A UV absorbent usable in the present invention will be described.

Examples of UV absorbents include an oxybenzophenone based compound, a benzotriazol based compound, a salicylic acid ester based compound, a benzophenone based compound, a cyanoacrylate based compound and a nickel complex salt, but these compounds are not limited thereto. UV absorbents other than these compounds are also usable.

Examples of these compounds will be given below.

-   UV-1: 2-(2′-hydroxy-5′-methylphenyl) benzotriazole -   UV-2: 2-(2′-hydroxy-3′,5′-di-tert-butylphenyl) benzotriazole -   UV-3: 2-(2′-hydroxy-3′-tert-butyl-5′-methylphenyl) benzotriazole -   UV-4: 2-(2′-hydroxy-3′,5′-di-tert-butylphenyl)-5-chlorobenzotriazole -   UV-5: 2-(2′-hydroxy-3′-(3″,4″,5″,6″-tetrahydro     phthalimidomethyl)-5′-methylphenyl) benzotriazole -   UV-6: 2,2-methylenebis     (4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazole-2-yl) phenol) -   UV-7:     2-(2′-hydroxy-3′-tert-butyl-5′-methylphenyl)-5-chlorobenzotriazole -   UV-8: 2,4-dihydroxybenzophenone -   UV-9: 2,2′-dihydroxy-4-methoxybenzophenone -   UV-10: 2-hydroxy-4-methoxy-5-sulfobenzophenone -   UV-11: Bis(2-methoxy-4-hydroxy-5-benzoylphenylmethane)     Usable is a UV absorbent in which UV absorption power is excellent     at a wavelength of at most 370 nm, together with less absorption of     visible light at a wavelength of at least 400 nm in view of     excellent liquid crystal display ability. It is preferred that UV     absorption power of an optical film in the present invention is not     more than 10% in transmittance with respect to light at a wavelength     of 380 nm, more preferably less than 6%, and most preferably from 0%     to less than 4%.

Regarding the content of a UV absorbent employed for an optical film, an appropriate addition amount is used according to setting of transmittance of light at a wavelength of 380 nm.

As antioxidants, hindered phenol compounds are also preferably employed. Examples of the compounds include 2,6-di-t-butyl-p-cresol, pentaerythityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,4-bis(n-octyl)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, 2,2-thio-diethylene-bis[3-(3,5-t-butyl-4-hydroxyphenyl)propionate, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, N,N′-hexamethylene-bis(3,5-di-t-butyl-4-hydroxy-4-hydroxy-hydrocinnamide), 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene and tris(3,5-di-t-butyl-4-hydroxybenzyl)-isocyanurate. Specifically, 2,6-di-t-butyl-p-cresol, pentaerythityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] and triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] are preferred. A hydrazine metal inactivation agent such as N,N′-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine and a phosphor processing stabilizing agent such as tris(2,4-di-t-butylphenyl)phosphite may be used in combination. The adding amount of these compounds is preferably 1 ppm to 1.0%, and more preferably from 10 ppm to 1,000 ppm, by weight based on the weight of the cellulose ester.

The anti-oxidizing agent is also called a deterioration-preventing agent. When a liquid crystal display is stored at high-temperature and humidity, the cellulose ester film may deteriorate. The anti-oxidizing agent is preferably contained in the foregoing cellulose ester film since halogen contained in the residual solvent amount in the cellulose ester film or a phosphoric acid in a phosphoric acid based plasticizer retards or prevents decomposition.

A uniform optical film in which no unevenness in each of layers is produced can be obtained, when a multi-layered film is also prepared by a manufacturing method of the present invention.

An optical film composed of thin layers having various functions can be provided in the present invention.

In the present invention, a layer having a thickness of 1-2 μm, on which electrically conductive resin particles such as metal oxide particles or cross-linked cation polymer particles are coated may also be provided as an anti-static layer or an electrically conductive layer.

An optical film prepared by a manufacturing method of the optical thin layer in the present invention is employed particularly as a polarizing plate protective film to produce a polarizing plate by a commonly known method. This optical film has excellent evenness in thin layers, so that it is preferably usable for various display devices, resulting in excellent display performance.

A hard coat layer, an anti-glare layer, an antireflection layer, an anti-static layer, an eclectically conductive layer, an optical diffusion layer, an adhesion increasing layer, an anti-stain layer, an orientation layer, a liquid crystal layer, an optical anisotropic layer and the like can be provided for an optical film of the present invention as the functional layer singly or appropriately in combination, if desired. Specifically, an actinic radiation curable resin layer is preferably used as a hard coat layer, and of the foregoing layers, an anti-reflection layer and an actinic radiation curable resin layer are preferable as the functional layer.

It is preferable that a substrate containing liquid crystal is generally placed between two polarizing plates in a liquid crystal display device, but it is particularly preferable that the polarizing plates are utilized in the area since a hard coat layer, an anti-glare layer, an antireflection layer and so forth are formed particularly in a polarizing plate protective film provided on the outer-most surface on the display side of a liquid crystal display device.

(Hard Coat Layer)

It is preferred that a long-length film in which treatment relating to the present invention is conducted has a hard coat layer as a functional layer.

An optical film of the present invention has an anti-reflection layer (high refractive index layer, low refractive index layer and the like) provided on the hard coat layer, and constitutes an anti-reflection film.

An actinic radiation curable resin layer is preferably used as a hard coat layer as described above.

An actinic radiation curable resin layer refers to a layer mainly containing a resin which can be cured through a cross-linking reaction caused by irradiating with actinic radiation such as UV rays or electron beams. A composition containing monomers having an ethylenic unsaturated double bond is preferably utilized to form a hard coat layer by hardening the composition with irradiating actinic radiation such as UV rays or electron beams. Typical examples of the actinic radiation curable resin include a UV curable resin and an electron beam curable resin, but a UV curable resin is preferably usable.

Examples of the UV curable resin include a UV curable urethane acrylate resin, a UV curable polyester acrylate resin, a UV curable epoxy acrylate resin, a UV curable polyol acrylate resin and a UV curable epoxy resin.

The UV curable urethane acrylate resin includes compounds which are generally prepared easily by, initially, reacting polyester polyol with a monomer or a prepolymer of isocyanate, followed by further reacting the product with an acrylate monomer having a hydroxy group such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate (herinafter, only acrylates are described, however methacrylates are also included) and 2-hydroxypropyl acrylate. For example, a compound disclosed in Japanese Patent O.P.I. Publication No. 59-151110 is preferably used.

For example, a mixture of 100 parts of UNIDIC 17-806 (Dainippon Ink and Chemicals, Inc.) and 1 part of COLONATE L (Nippon Polyurethane Industry Co., Ltd.) is preferably used.

The UV curable polyester acrylate resins include compounds which are generally prepared easily by reacting a polyester polyol with a 2-hydroxyethyl acrylate monomer or a 2-hydroxy acrylate monomer. For example, those disclosed in Japanese Patent O.P.I. Publication No. 59-151112 are preferably used.

The UV curable epoxy acrylate resin includes compounds prepared by reacting an epoxy acrylate oligomer with a reactive dilutant and a photoreaction initiatoras, which are preferably usable, as described in Japanese Patent O.P.I. Publication No. 1-105738.

Examples of the UV curable polyol acrylate resin include trimethylol propane triacrylate, ditrimethylol propane tetracrylate, pentaerythritol triacrylate, pentaerythritol tetracrylate, dipentaerythritol hexaacrylate and alkyl modified dipentaerythritol pentaacrylate.

Examples of the photopolymerization initiators include benzoine including derivatives, acetophenone, benzophenone, hydroxy benzophenone, Michler's ketone, α-amyloxim ester,thioxanthone and derivatives thereof. These compounds may be utilized together with a photosensitizer. The photopolymerization initiator described above can also be utilized as a photosensitizer. Further, sensitizers such as n-butyl amine, triethyl amine and tri-n-butyl phosphine can be utilized together with an epoxy acrylate photopolymerization agent. The amount of a photopolymerization initiator or a photosensitizer used for a UV curable resin composition is preferably 0.1-15 parts by weight, more preferably 1-10 parts by weight with respect to 100 parts by weight of the composition.

Resin monomers include, for example: (i) a monomer having one unsaturated double bond, such as methyl acrylate, ethyl acrylate, isopropyl acrylate, butyl acrylate, benzyl acrylate, cyclohexyl acrylate, vinyl acetate and styrene, and (ii) a monomer having at least two unsaturated double bonds, such as ethyleneglycol diacrylate, propyleneglycol diacrylate, divinyl benzene, 1,4-cyclohexyane diacrylate and 1,4-cyclohexyldimethyl diacrylate. The foregoing trimethylolpropane triacrylate and pentaerythritol tetraacrylate ester can also be included.

Products available on the market as a UV curable resin usable in the present invention are: Adekaoptomer KR•BY Series such as KR-400, KR-410, KR-550, KR-566, KR-567 and BY-320B (manufactured by Asahi Denka Co., Ltd.); Koeihard A-101-KK, A-101-WS, C-302, C-401-N, C-501, M-101, M-102, T-102, D-102, NS-101, FT-102Q8, MAG-1-P20, AG-106 and M-101-C (manufactured by Koei Kagaku Co., Ltd.); Seikabeam PHC2210(S), PHC X-9(K-3), PHC2213, DP-10, DP-20, DP-30, P1000, P1100, P1200, P1300, P1400, P1500, P1600, SCR900 (manufactured by Dainichiseika Kogyo Co., Ltd.); KRM7033, KRM7039, KRM7130, KRM7131, UVECRYL29201 and UVECRYL29202 (manufactured by Daicel U. C. B. Co., Ltd.); RC-5015, RC-5016, RC-5020, RC-5031, RC-5100, RC-5102, RC-5120, RC-5122, RC-5152, RC-5171, RC-5180 and RC-5181 (manufactured by Dainippon Ink & Chemicals, Inc.); Olex No.340 Clear (manufactured by Chyugoku Toryo Co., Ltd.); Sunrad H-601, RC-750, RC-700, RC-600, RC-500, RC-611 and RC-612 (manufactured by Sanyo Kaseikogyo Co., Ltd.); SP-1509 and SP-1507 (manufactured by Syowa Kobunshi Co., Ltd.); RCC-15C (manufactured by Grace Japan Co., Ltd.) and Aronix M-6100, M-8030 and M-8060 (manufactured by Toagosei Co., Ltd.).

Specific examples include trimethylol propane triacrylate, ditrimethylol propane tetracrylate, pentaerythritol triacrylate, pentaerythritol tetracrylate, dipentaerythritol hexaacrylate and alkyl modified dipentaerythritol pentaacrylate.

These actinic radiation curable resin layers can be prepared by commonly known methods such as a gravure coater, a dip coater, a reverse coater, a wire bar coater, a die coater and ink jet printing.

Light sources to cure layers of UV curable resin via photo-curing reaction are not specifically limited, and any light source may be used if UV ray is generated. For example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a carbon arc lamp, a metal halide lamp and a xenon lamp may be utilized. Though the exposure condition depends on the type of lamp, the exposure quantity of actinic radiation is preferably 5-500 mJ/cm², and more preferably 20-150 mJ/cm².

It is preferred that oxygen concentration at the exposure portion is also reduced to be 0.01-2% under a nitrogen purge.

It is preferred that actinic radiation exposure is conducted while applying tension in the direction transporting a film, and more preferred that it is conducted while applying tension in the lateral direction. The applied tension is preferably 30-300 N/m. The method of applying tension is not specifically limited. The tension may be applied in the transporting direction on a backroll, or applied in the lateral direction or in the biaxial directions employing a tenter, whereby a film having further improved flatness can be obtained.

Examples of organic solvents used for UV curable resin layer composition coating solution include hydrocarbons (toluene and xylene), alcohols (methanol, ethanol, isopropanol, butanol and cyclohexanol), ketones (acetone, methyl ethyl ketone and methyl isobutyl ketone), esters (methyl acetate, ethyl acetate and methyl lactate), glycol ethers and other organic solvents. These organic solvents may be also used in combination. The above-described organic solvents preferably contain propylene glycol monoalkyl ether (the alkyl having 1-4 carbon atoms) or propylene glycol monoalkyl ether acetate (the alkyl having 1-4 carbon atoms) of at least 5% by weight, and more preferably 5-80% by weight.

In a coating solution of a UV curable resin, a silicon compound such as a polyether modified silicone oil, is preferably added. The number average molecular weight of the polyether modified silicone oil is preferably from 1000 to 100000 and more preferably from 2000 to 50000. Addition of the polyether modified silicone oil with a number average molecular weight of less than 1000 may lower the drying rate of the coating solution, while that of more than 100000 may be difficult to bleed out at the surface of the coated film.

Silicon compounds available on the market include, for example: DKQ8-779 (a trade name of Dow Corning Corp.), SF3771, SF8410, SF8411, SF8419, SF8421, SF8428, SH200, SH510, SH1107, SH3771, BX16-034, SH3746, SH3749, SH8400, SH3771M, SH3772M, SH3773M, SH3775M, BY-16-837, BY-16-839, BY-16-869, BY-16-870, BY-16-004,BY-16-891, BY-16-872, BY-16-874, BY22-008M, BY22-012M, FS-1265 (all being trade names of Dow Corning Toray Silicone Co., Ltd.), KF-101, KF-1OOT, KF351, KF352, KF353, KF354, KF355, KF615, KF618, KF954, KF6004, siliconeX-22-945, X22-160AS (all being trade names of Shin-Etsu Chemical Co., Ltd.), XF3940, XF3949 (both being trade names of Toshiba Silicones Co., Ltd.), DISPARLONLS-009 (a trade name of Kusumoto Chemicals Ltd.), GLANOL410 (a trade name of Kyoeisha Chemicals Co., Ltd.), TSF4440, TSF4441, TSF4445, TSF4446, TSF4452, TSF4460 (all being trade names of GE Toshiba Silicones Co., Ltd.), BYK-306, BYK-330, BYK-307, BYK-341, BYK-361 (all being trade names of BYK-Chemie Japan KK), L Series (L-7001, L-7006, L-7604 and L-9000), Y Series and FZ Series (FZ-2203, FZ-2206 and FZ-2207) (all from Nippon Unicar Co., Ltd.).

These compositions may improve the coating ability of a coating solution onto a substrate or an under coat layer. These compounds used in the top layer of film may contribute to improvement of scratch resistance of the film as well as water repellency, oil repellency and anti-stain properties of the film. The content of the silicon compound is preferably from 0.01 to 3% by weight based on the solid components in the coating solution.

The forgoing coating methods are also used as coating method of a UV curable resin layer coating solution. The wet thickness of the coated UV curable resin layer is preferably 0.1-30 μm and more preferably 0.5-15 μm. The dry thickness of the coated UV curable resin layer is preferably 0.1-20 μm and more preferably 1-10 μm.

The UV curable resin layer is preferably exposed to UV rays during or after drying. The duration of UV ray irradiation is preferably from 0.1 seconds to 5 minutes in order to secure the exposure amount of 5-150 mJ/cm² as mentioned above. In view of working efficiency and hardening efficiency of the UV curable resin layer, the duration is more preferably 0.1-10 seconds.

Intensity at the actinic radiation portion is preferably 50-150 mW/cm².

The UV curable resin layer thus obtained may preferably contain inorganic or organic particles in order to attain the following characteristics: (i) preventing blocking, (ii) improving scratch resistance, (iii) providing an antiglare property or a light diffusion property and (iv) optimizing the refractive index.

The hard coat layer of the present invention preferably contains inorganic particles, examples of which include, for example: silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, magnesium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate. Among these, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, magnesium oxide are specifically preferable.

Organic particles include, for example: particles of polymethacrylic acid methyl acrylate resin, acryl styrene based resin, polymethyl methacrylate resin, silicon based resin, polystyrene based resin, polycarbonate resin, benzoguanamine based resin, melamine based resin, polyolefin based resin, polyester based resin, polyamide based resin, polyimide based resin and polyfluorinated ethylene based resin. Specifically preferable organic particles include, for example: particles of cross-linked polystylene (such as SX-130H, SX-200H and SX-350H manufactured by Soken Chemical & Engineering Co., Ltd.) and polymethyl methacrylate (such as MX150 and MX300 manufactured by Soken Chemical & Engineering Co., Ltd.).

The average particle diameter of the particles is preferably 0.005-5 μm, and more preferably 0.01-1 μm. The particle content of the hard coat layer is preferably 0.1-30 parts by weight per 100 parts by weight of the UV curable resin composition.

It is preferred that the UV curable resin layer is a clear hard coat layer having a center line average roughness (Ra prescribed by JIS B 0601) of 1-50 nm or an anti-glare layer having an Ra value of 0.1-1 μm. The center line average roughness (Ra) is preferably measured by means of a surface roughness meter using interference of light, for example, RST/PLUS manufactured by WYKO Co., Ltd.

The hard coat layer of the present invention may preferably contain an antistatic agent. For example, preferable are an electrically conductive material containing as a main ingredient at least one of the elements selected from the group of Sn, Ti, In, Al, Zn, Si, Mg, Ba, Mo, W and V, and having a volume resistivity of not more than 10⁷ Ω·cm.

Examples of the antistatic agent also include: oxides and composite oxides of the above described elements.

Examples of a metal oxide include: ZnO, TiO₂, SnO₂, Al₂O₃, In₂O₃, SiO₂, MgO, BaO, MoO₂, V₂O₅ and composite metal oxides thereof. Of these, specifically preferable are, for example, ZnO, In₂O₃, TiO₂, and SnO₂. As examples of indroduction of foreign element, effective are, (i) introduction of, for example, Al or In in ZnO; (ii) introduction of, for example, Nb or Ta in TiO₂; and (iii) introduction of, for example, Sb, Nb or a halogen atom in SnO₂. The amount of the foreign element is preferably 0.01-25mol% and specifically preferably 0.1-15mol %. The volume resistivity of these conductive metal oxide powder is preferably at most 10⁷ Ω·cm and specifically preferably at most 10⁵ Ω·cm.

A UV curable resin layer having a convexoconcave structure is provided by using an embossing method employing a cast mold roll (embossing roll) having a convexoconcave structure formed on the surface, and it is also preferable that this is an anti-glare layer.

It is preferable that an anti-reflection layer is provided as a functional layer further on the above-described hard coat layer in an optical film of the present invention, and preferably a low refractive index layer particularly containing hollow particles.

(Low Refractive Index Layer)

It is preferable that the low refractive index layer contains hollow particles, and more preferable that it contains silicon alkoxide, a silane coupling agent and a hardener other than hollow particles.

<Hollow Particle>

It is preferable that the following hollow particles are contained in a low refractive index layer.

Hollow silica particles described here are (I) composite particles composed of a porous particle and a coated layer arranged on the surface of the porous particle or (II) hollow particles, the interior of which is hollow and the hollow is filled with contents such as a solvent, a gas or a porous substance. Herein, at least either (I) composite particles or (II) hollow particles is contained in a low refractive index layer, or the both of them may be contained.

Herein, hollow particles are particles the interior of which is hollow, and the hollow is surrounded by a particle wall. The interior of the hollow is filled with the contents such as a solvent, a gas or a porous substance which have been utilized in preparation. The mean particle diameter of such hollow particles is preferably in a range of 5-300 nm and preferably of 10-200 nm. The mean particle diameter of hollow particles utilized is appropriately selected depending on the thickness of the formed transparent coated film and is preferably in a range of ⅔- 1/10 of the layer thickness of the transparent coated film of such as a formed low refractive index layer. These inorganic particles are preferably utilized in a state of being dispersed in a suitable medium to form a low refractive index layer. As dispersing medium, water, alcohol (such as methanol, ethanol and isopropanol), ketone (such as methyl ethyl ketone and methyl isobutyl ketone) and ketone alcohol (such as diacetone alcohol) are preferable.

A thickness of the coated layer of a composite particle or the thickness of the particle wall of a hollow particle is preferably in a range of 1-20 nm and more preferably in a range of 2-15 nm. In the case of a composite particle, when a thickness of the coated layer is less than 1 nm, a particle may not be completely covered, whereby effects of a low refractive index may not be obtained. Further, when a thickness of the coated layer exceeds 20 nm, the porosity (a micro-pore volume) of a composite particle may be decreased, resulting in insufficient effects of a low refractive index. Further, in the case of a hollow particle, particle shape may not be hold when a thickness of the particle wall is less than 1 nm, while effects of a low refractive index may not be obtained when a thickness of the particle wall exceeds 20 nm.

The coated layer of a composite particle or the particle wall of a hollow particle is preferably made of silica as a primary component. Further, components other than silica may be incorporated in the coated layer of a composite particle or the particle wall of a hollow particle, and specific examples include such as Al₂O₃, B₂O₃, TiO₂, ZrO₂, SnO₂, CeO₂, P₂O₃, Sb₂O₃, MoO₃, ZnO₂, and WO₃. A porous particle to constitute a composite particle includes those comprised of silica, those comprised of silica and an inorganic compound other than silica and those comprised of such as CaF₂, NaF, NaAlF₆ and MgF. Among them, specifically preferable is a porous particle comprised of a complex oxide of silica and an inorganic compound other than silica. An inorganic compound other than silica includes one type or at least two types of such as Al₂O₃, B₂O₃, TiO₂, ZrO₂, SnO₂, CeO₂, P₂O₃, Sb₂O₃, MoO₃, ZnO₂ and WO₃. In such a porous particle, mole ratio MO_(x)/SiO₂ is preferably in a range of 0.0001-1.0 and more preferably of 0.001-0.3 when silica is represented by SiO₂ and an inorganic compound other than silica is represented by an equivalent oxide (MO_(x)). A porous particle having mole ratio MO_(x)/SiO₂ of less than 0.0001 is difficult to be prepared, and no conductivity is generated even though it is prepared. Further, when mole ratio MO_(x)/SiO₂ of a porous particle exceeds 1.0, a silica ratio becomes small, whereby it may be further difficult to prepare a particle having a low refractive index, together with a small pore volume.

A pore volume of such a porous particle is preferably in a range of 0.1-1.5 ml/g and more preferably of 0.2-1.5 ml/g. When the pore volume is less than 0.1 ml/g, a particle having a sufficiently decreased refractive index cannot be prepared, while, when it exceeds 1.5 ml/g, strength of a particle is decreased and strength of the resulting coated film may be decreased.

Herein, the pore volume of such a porous particle can be determined by a mercury pressurized impregnation method. Further, a content of a hollow particle includes such as a solvent, a gas and a porous substance which have been utilized at preparation of the particle. In a solvent, such as a non-reacted substance of a particle precursor which is utilized at hollow particle preparation and a utilized catalyst may be contained. Further, a porous substance includes those comprising compounds exemplified in the aforesaid porous particle. These contents may be those containing single component or mixture of plural components.

As a manufacturing method of such inorganic particles, a preparation method of composite oxide colloidal particles, disclosed in paragraph Nos. [0010]-[0033] of Japanese Patent O.P.I. Publication No. 7-133105, is suitably applied. Specifically, in the case of a composite particle being comprised of silica and an inorganic compound other than silica, the inorganic particle is manufactured according to the following first-third processes.

First Process: Preparation of Porous Particle Precursor

In the first process, alkaline aqueous solutions of a silica raw material and of an inorganic compound raw material other than silica are independently prepared or a mixed aqueous solution of a silica raw material and an inorganic compound raw material other than silica is prepared, in advance, and this aqueous solution is gradually added into an alkaline aqueous solution having a pH of not less than 10 while stirring depending on the composite ratio of the aimed composite oxide, whereby a porous particle precursor is prepared.

As a silica raw material, silicate of alkali metal, ammonium or organic base is utilized. As silicate of alkali metal, utilized are sodium silicate (water glass) and potassium silicate. organic base includes quaternary ammonium salt such as tetraethylammonium salt; and amines such as monoethanolamine, diethanolamine and triethanolamine. Herein, an alkaline solution, in which such as ammonia, quaternary ammonium hydroxide or an amine compound is added to a silicic acid solution, is also included in silicate of ammonium or silicate of organic base.

Further, as a raw material of an inorganic compound other than silica, utilized is the foregoing alkali-soluble electrically conductive compound.

The pH value of a mixed aqueous solution changes simultaneously with addition of these aqueous solutions, however, operation to control the pH value into a specific range is not necessary. The aqueous solution finally takes a pH value determined by the types and the mixing ratio of inorganic oxide. At this time, the addition rate of an aqueous solution is not specifically limited. Further, dispersion of a seed particle may be also utilized as a starting material at the time of manufacturing of composite oxide particles. Said seed particles are not specifically limited, however, particles of inorganic oxide such as SiO₂, Al₂O₃, TiO₂ or ZrO₂ or composite oxide thereof are utilized, and generally sol thereof can be utilized. Further, a porous particle precursor dispersion prepared by the aforesaid manufacturing method may be utilized as a seed particle dispersion. In the case of utilizing a seed particle dispersion, after the pH of a seed particle dispersion is adjusted to not lower than 10, an aqueous solution of the aforesaid compound is added into said seed particle dispersion while stirring. In this case pH control of dispersion is not necessarily required. By utilizing seed particles in this manner, it is easy to control the particle diameter of prepared particles and particles having a uniform size distribution can be obtained.

A silica raw material and an inorganic compound raw material, which were described above, have a high solubility at alkaline side. However, when the both are mixed in pH range showing this high solubility, the solubility of an oxoacid ion such as a silicic acid ion and an aluminic acid ion will decrease, resulting in precipitation of these composite products to form particles or to be precipitated on a seed particle causing particle growth. Therefore, at the time of precipitation and growth of particles, pH control in a conventional method is not necessarily desired.

A composite ratio of silica and an inorganic compound other than silica is preferably in a range of 0.05-2.0 and more preferably of 0.2-2.0, based on mole ratio MO_(x)/SiO₂, when an inorganic compound other than silica is converted to oxide (MO_(x)). In this range, the smaller is the ratio of silica, increases the pore volume of porous particles. However, a pore volume of porous particles barely increases even when the mole ratio exceeds 2.0. On the other hand, a pore volume becomes small when the mole ratio is less than 0.05. In the case of preparing hollow particles, mole ratio of MO_(x)/SiO₂ is preferably in a range of 0.25-2.0.

Second Process: Removal of Inorganic Compounds Other Than Silica from Porous Particles

In the second process, at least a part of inorganic compounds other than silica (elements other than silica and oxygen) is selectively removed from the porous particle precursor prepared in the aforesaid first process. As a specific removal method, inorganic compounds in a porous particle precursor are dissolved and removed by use of such as mineral acid and organic acid, or by being contacted with cationic ion-exchange resin.

Herein, a porous particle precursor prepared in the first process is a particle having a network structure in which silica and an inorganic compound element bond via oxygen. In this manner, by removing inorganic compounds (elements other than silica and oxygen) from a porous particle precursor, porous particles, which are more porous and have a large pore volume, can be prepared. Further, hollow particles can be prepared by increasing the removal amount of inorganic compound (elements other than silica and oxygen) from a porous particle precursor.

Further, in advance to removal of inorganic compounds other than silica from a porous particle precursor, it is preferable to form a silica protective film via addition of a silicic acid solution prepared by dealkalization of alkali metal salt of silica; or a hydrolyzable organosilicon compound, in a porous particle precursor dispersion prepared in the first process. The thickness of a silica protective film is 0.5-15 nm. Herein, even when a silica protective film is formed, since the protective film in this process is porous and has a thin thickness, it is possible to remove the aforesaid inorganic compounds other than silica from a porous particle precursor.

By forming such a silica protective film, the foregoing inorganic compounds other than silica can be removed from a porous particle precursor while keeping the particle shape as it is. Further, at the time of forming a silica cover layer described later, the pore of porous particles is not blocked by a cover layer, and thereby the silica cover layer described later can be formed without decreasing the pore volume. Herein, when the amount of inorganic compound to be removed is small, it is not necessary to form a protective film because the particles will never be broken.

Further, in the case of preparation of hollow particles, it is preferable to form this silica protective film. At the time of preparation of hollow particles, a hollow particle precursor, which is comprised of a silica protective film, a solvent and insoluble porous solid within said silica protective film, is obtained when inorganic compounds are removed, and hollow particles are formed, by making a particle wall from a formed cover layer, when the cover layer described later is formed on the hollow particle precursor.

The amount of a silica source added to form the aforesaid silica protective film is preferably in a range to maintain the particle shape. When the amount of a silica source is excessively large, it may become difficult to remove inorganic compounds other than silica from a porous particle precursor because a silica protective film becomes excessively thick. As a hydrolizable organosilicon compound utilized to form a silica protective film, alkoxysilane represented by formula R_(n)Si(OR′)⁴⁻¹ [R, R′: a hydrocarbon group such as an alkyl group, an aryl group, a vinyl group and an acryl group; n=0, 1, 2 or 3] can be utilized. Specifically, fluorine-substituted tetraalkoxysilane, such as tetramethoxysilane, tetraethoxysilane and tetraisopropoxysilane, is preferably utilized.

As an addition method, a solution, in which a small amount of alkali or acid as a catalyst is added into a mixed solution of these alkoxysilane, pure water and alcohol, is added into the aforesaid dispersion of porous particles, and silicic acid polymer formed by hydrolysis of alkoxysilane is precipitated on the surface of inorganic oxide particles. At this time, alkoxysilane, alcohol and a catalyst may be simultaneously added into the dispersion. As an alkali catalyst, ammonia, hydroxide of alkali metal and amines can be utilized. Further, as an acid catalyst, various types of inorganic acid and organic acid can be utilized.

In the case that a dispersion medium of a porous particle precursor is water alone or has a high ratio of water to an organic solvent, it is also possible to form a silica protective film by use of a silicic acid solution. In the case of utilizing a silicic acid solution, a predetermined amount of a silicic acid solution is added into the dispersion and alkali is added simultaneously, to precipitate silicic acid solution on the porous particle surface. Herein, a silica protective film may also be formed by utilizing a silicic acid solution and the aforesaid alkoxysilane in combination.

Third Process: Formation of Silica Cover Layer

In the third process, by addition of such as a hydrolyzable organosilicon compound or a silicic acid solution, into a porous particle dispersion (into a hollow particle dispersion in the case of hollow particles), which is prepared in the second process, the surface of particles is covered with a polymer substance of such as a hydrolyzable organosilicon compound or a silicic acid solution to form a silica cover layer.

As a hydrolyzable organosilicon compound utilized for formation of a silica cover layer, alkoxysilane represented by formula R_(n)Si(OR′)_(4−n) [R, R′: a hydrocarbon group such as an alkyl group, an aryl group, a vinyl group and an acryl group; n=0, 1, 2 or 3] , as described before, can be utilized. Specifically, tetraalkoxysilane such as tetramethoxysilane, tetraethoxysilane and tetraisopropoxysilane are preferably utilized.

As an addition method, a solution, in which a small amount of alkali or acid as a catalyst is added into a mixed solution of these alkoxysilane, pure water and alcohol, is added into the aforesaid dispersion of porous particles (a hollow particle precursor in the case of hollow particles), and silicic acid polymer formed by hydrolysis of alkoxysilane is precipitated on the surface of porous particles (a hollow particle precursor in the case of hollow particles). At this time, alkoxysilane, alcohol and a catalyst may be simultaneously added into the dispersion. As an alkali catalyst, ammonia, hydroxide of alkali metal and amines can be utilized. Further, as an acid catalyst, various types of inorganic acid and organic acid can be utilized.

In the case that a dispersion medium of porous particles (a hollow particle precursor in the case of hollow particles) is water alone or a mixed solution of water with an organic solvent having a high ratio of water to an organic solvent, it is also possible to form a coated layer by using a silicic acid solution. A silicic acid solution is an aqueous solution of lower polymer of silicic acid which is formed by ion-exchange and dealkalization of an aqueous solution of alkali metal silicate such as water glass.

A silicic acid solution is added into a dispersion of porous particles (a hollow particle precursor in the case of hollow particles), and alkali is simultaneously added to precipitate silicic acid lower polymer on the surface of porous particles (a hollow particle precursor in the case of hollow particles). Herein, silicic acid solution may be also utilized in combination with the aforesaid alkoxysilane to form a coated layer. The addition amount of an organosilicon compound or a silicic acid solution, which is utilized for coated layer formation, is as much as to sufficiently cover the surface of colloidal particles and the solution is is added into a dispersion of porous particles (a hollow particle precursor in the case of hollow particles) at an amount to make a thickness of the finally obtained silica coated layer of 1-20 nm. Further, in the case that the aforesaid silica protective film is formed, an organosilicon compound or a silicic acid solution is added at an amount to make a thickness of the total of a silica protective film and a silica coated layer of 1-20 nm.

Next, a dispersion of particles provided with a coated layer is subjected to thermal treatment. By thermal treatment, in the case of porous particles, a silica coated layer, which covers the surface of porous particles, becomes minute to prepare a dispersion of composite particles comprising porous particles covered with a silica coated layer. Further, in the case of a hollow particle precursor, the formed coated layer becomes minute to form a hollow particle wall, whereby a dispersion of hollow particles provided with a hollow, the interior of which is filled with a solvent, a gas or a porous solid, is prepared.

Thermal treatment temperature at this time is not specifically limited provided being so as to block fine pores of a silica coated layer, and is preferably in a range of 80-300° C. At a thermal treatment temperature of lower than 80° C., a silica coated layer may not become minute to completely block the fine pores or the treatment time may become long. Further, when a prolonged treatment at a thermal treatment temperature of higher than 300° C. is performed, particles may become minute and an effect of a low refractive index may not be obtained.

A refractive index of inorganic particles prepared in this manner is as low as less than 1.44. It is assumed that the refractive index becomes low because such inorganic particles maintain porous property in the interior of porous particles or the interior is hollow.

It is preferable that other than minute hollow particles, the low refractive index layer incorporates hydrolyzed products of alkoxysilicon compounds and condensation products which are formed via the following condensation reaction. It is particularly preferable to incorporate a SiO₂ sol prepared employing the alkoxysilicon compounds represented by following Formula (3) and/or (4) or hydrolyzed products thereof. R1-Si(OR2)₃  Formula (3) Si(OR2)₄  Formula (4) wherein R1 represents a methyl group, an ethyl group, a vinyl group, or an organic group incorporating an acryloyl group, a methacryloyl group, an amino group, or an epoxy group, and R2 represents an methyl group or an ethyl group.

Hydrolysis of silicon alkoxide and silane coupling agents is performed by dissolving the above in suitable solvents. Examples of used solvents include ketones such as methyl ethyl ketone, alcohols such as methanol, ethanol, isopropyl alcohol, or butanol, esters such as ethyl acetate, or mixtures thereof.

Water in a slightly larger amount for hydrolysis is added to a solution prepared by dissolving the above silicon alkoxide or silane coupling agents in solvents, and the resulting mixture is stirred at 15-35° C. but preferably 20-30° C. for 1-48 hours but preferably 3-36 hours.

It is preferable to employ catalysts during the above hydrolysis. Preferably employed as such catalysts are acids such as hydrochloric acid, nitric acid, or sulfuric acid. These acids are employed in the form of an aqueous solution at a concentration of 0.001-20.0 N, but preferably 0.005-5.0 N. It is possible to employ water in the above aqueous catalyst solution as water for hydrolysis.

Alkoxysilicon compounds undergo hydrolysis over the specified period of time, and the hydrolyzed alkoxysilicon solution is diluted with solvents, followed by the addition of other necessary additives, whereby a low refractive index layer liquid coating composition is prepared. It is possible to form a low refractive index layer on a substrate by applying the above liquid coating composition onto a substrate such as a film followed by drying.

<Alkoxysilicon Compound>

In the present invention, preferred as alkoxysilicon compounds (hereinafter also referred to as alkoxysilanes) employed to prepare the low refractive index layer liquid coating composition are those represented by following Formula (5). R(4−n)Si(OR′)n  Formula (5) wherein R′ represents an alkyl group; R represents a hydrogen atom or a monovalent substituent; and n is 3 or 4.

The alkyl groups represented by R′ include groups such as a methyl group, an ethyl group, a propyl group, or a butyl group, which may have a substituent. The substituents are not particularly limited as long as characteristics as an alkoxysilane are maintained. Examples of such substituents include a halogen atom such as fluorine and an alkoxy group, but unsubstituted alkyl groups are more preferred. Particularly preferred are a methyl group and an ethyl group.

The monovalent substituents represented by R are not particularly limited, and examples include an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an aromatic heterocyclyl group, and a silyl group. Of these, preferred are an alkyl group, a cycloalkyl group, and an alkenyl group. These may be further substituted. Cited as substituents of R are a halogen atom such as a fluorine atom or a chlorine atom, an amino group, an epoxy group, a mercapto group, a hydroxyl group, and an acetoxy group. Preferable examples of the alkoxysilane specifically represented by the above formula include tetramethoxysilane, tetraethoxysilane (TEOS), tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetra-t-butoxysilane, tetrakis(methoxyethoxy)silane, tetrakis(methoxypropoxy)silane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-butyltrimethoxysilane, i-butyltrimethoxysilane, n-hexyltrimethoxysilane, 3-glycydoxyproyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, acetoxytriethoxysilane, (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trimethoxysilane, (3,3,3-trifluoropropyl)trimethoxysilane, (3,3,3-trifluoropropyl)trimethoxysilane, pentafluorophenylpropyltrimethoxysilane, further vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane.

Further, included may be silicon compounds in the form of oligomers such as SILICATE 40, SILICATE 45, SILICATE 48, and M SILICATE 51, produced by Tamagawa Chemical Co., which are partial condensation products of the above compounds.

Since the above alkoxysilanes incorporate silicon alkoxide group capable of undergoing hydrolysis polycondensation, the network structure of polymer compounds is formed in such a manner that these alkoxysilanes undergo hydrolysis, condensation and crosslinking. The resulting composition is employed as a low refractive index layer liquid coating composition which is applied onto a substrate and dried, whereby a layer uniformly incorporating silicon oxide is formed on the substrate.

It is possible to perform a hydrolysis reaction employing the method known in the art. Hydrophilic alkoxysilanes are dissolved in a mixture of water of the specified amount and hydrophilic organic solvents such as methanol, ethanol, or acetonitrile so that alkoxysilanes are compatible with solvents. After the addition of hydrolysis catalysts, alkoxysilanes undergo hydrolysis and condensation. By performing the hydrolysis and condensation reaction commonly at 10-100° C., silicate oligomers in a liquid state, having at least two hydroxyl groups, are formed, whereby a hydrolyzed liquid composition is prepared. It is possible to appropriately control the degree of hydrolysis varying the amount of employed water.

In the present invention, preferred as solvents added to alkoxysilanes together with water are methanol and ethanol since they are less expensive and form a layer exhibiting excellent characteristics and desired hardness. It is possible to employ isopropanol, n-butanol, isobutanol, and octanol, while the hardness of the resulting layer tends to decrease. The amount of solvents is commonly 50-400 parts by weight with respect to 100 parts by weight of tetraalkoxysilanes prior to hydrolysis, but is preferably 100-250 parts by weight.

The hydrolyzed liquid composition is prepared as described above. The above composition is diluted with solvents, and if desired, added with additives. Subsequently, components required to form a low refractive index layer liquid coating composition are mixed, whereby a low refractive index layer liquid coating composition is prepared.

Cited as hydrolysis catalysts may be acids, alkalis, organic metals, and metal alkoxides. In the present invention, preferred are inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, hypochlorous acid, or boric acid, or organic acids. Of these, particularly preferred are nitric acid, carboxylic acids such as acetic acid, polyacrylic acid, benzenesulfonic acid,paratoluenesulfonic acid, and methylsulfonic acid. Of these, most preferably employed are nitric acid, acetic acid, citric acid, and tartaric acid. Other than above citric acid and tartaric acid, also preferably employed are levulinic acid, formic acid, propionic acid, malic acid, succinic acid, methylsuccinic acid, fumaric acid, oxalacetic acid, pyruvic acid, 2-oxoglutaric acid, glycolic acid, D-glyceric acid, D-gluconic acid, malonic acid, maleic acid, oxalic acid, isocitric acid, and lactic acid.

Of the above catalysts, preferred are those which do not remain in the layer via evaporation during drying and also exhibit a low boiling point. Accordingly, acetic acid and nitric acid are most preferred.

The addition amount is commonly 0.001-10 parts by weight with respect to 100 parts by weight of the employed alkoxysilicon compounds (for example, tetraalkoxysilane), but is preferably 0.005-5 parts by weight. Further, the addition amount of water is to be at least the amount capable of performing theoretically 100% hydrolysis of the compound to be hydrolyzed. It is recommended to add water in an equivalent amount of 100-300%, but preferably of 100-200%.

During the hydrolysis of the above alkoxysilanes, it is preferable to blend the following inorganic particles.

After initiation of hydrolysis, a hydrolyzed liquid composition is allowed to stand over the specified period of time. After the hydrolysis reaches the specified degree, the above catalysts are employed. The standing period refers to the sufficient period during which the above hydrolyses and crosslinking due to condensation are progressed to result in desired layer characteristics. The specific period varies depending on the type of acid catalysts, but when acetic acid is employed, the period is at least 15 hours at room temperature, while when nitric acid is employed, the period is preferably at least two hours. Ripening temperature affects ripening temperature. Generally, at a higher temperature, ripening is more promoted. However, since gelling occurs at more than or equal to 100° C., it is appropriate to raise and maintain the temperature between 20-60° C.

The silicate oligomer solution prepared by performing hydrolysis and condensation as described above is added with the above fine hollow particles and additives, and the resulting mixture is diluted as required, whereby a low refractive index layer liquid coating composition is prepared. Subsequently, the resulting coating composition is applied onto the above film, whereby it is possible to form a layer as a low refractive index layer composed of an excellent silicon oxide layer.

Further, in the present invention, other than the above alkoxysilanes, employed may be the compounds which are prepared by modifying silane compounds (being monomers, oligomers, or polymers) having a functional group such as an epoxy group, an amino group, an isocyanate group, or a carboxyl group, and may be employed individually or in combination.

(Fluorine Compounds)

The low refractive index layer employed in the present invention may be made of fluorine compounds, and it is preferable that it incorporates hollow particles and fluorine compounds.

It is also preferable to contain fluorine-containing resins (hereinafter also referred to as “pre-crosslinking fluorine containing resins”), which undergo crosslinking via heat or ionizing radiation. By incorporating the above fluorine containing resins, it is possible to provide a desired anti-stain anti-reflection film.

Preferably listed as such fluorine containing resins prior crosslinking may be fluorine containing copolymers which are formed employing fluorine containing vinyl monomers and monomers to provide a crosslinking group. Specific examples of the above fluorine containing vinyl monomer units include fluoroolefins (for example, fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, or perfluoro-2,2-dimethyl-1,3-dioxonol), and alkylester derivatives in which (meth)acrylic acid is partially or completely fluorinated (for example, VISCOAT 6FM (produced by Osaka Yuki Kagaku Co.), or M-2020 (produced by Daikin Co.), completely or partially fluorinated vinyl ethers. Cited as monomers to provide a crosslinking group are vinyl monomers which previously incorporate a crosslinking functional group in the molecule such as glycidyl methacrylate, vinyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, vinyl glycidyl ether, and in addition, vinyl monomers having a carboxyl group, a hydroxyl group, an amino group, or a sulfone group (for example, (meth)acrylic acid, methylol (meth)acrylate, hydroxyalkyl (meth)acrylate, allyl acrylate, hydroxyalkyl vinyl ether, or hydroxyalkyl allyl ether). Japanese patent O.P.I. Publication Nos. 10-25388 and 10-147739 describe that it is possible to introduce, after copolymerization, a crosslinking structure to the latter via the addition of compounds having a group capable of reacting with a functional group in the polymers and at least one reactive group. Examples of such crosslinking groups include an acryloyl, methacryloyl, isocyanate, epoxy, aziridine, oxazolidine, aldehyde, carbonyl, hydrazine, carboxyl, methylol, or active methylene group. Cases, in which fluorine containing polymers react with a crosslinking group upon being heated, or undergo crosslinking upon being heated via combinations such as an ethylenic unsaturated group and a thermally radical generating agent, or an epoxy group and a thermally acid generating agents, are designated as a thermal curing type. On the other hand, cases in which crosslinking is performed via combination of an ethylenic unsaturated group and a photolytically radical generating agent or an epoxy group and a photolytically acid generating agent upon being exposed to radiation (preferably ultraviolet radiation or electron beams), is designated as an ionizing radiation curable type.

In addition to the above monomers, employed as pre-crosslinking fluorine containing resins may be fluorine containing copolymers which are prepared simultaneously employing monomers other than the fluorine containing vinyl monomers and monomers to provide a crosslinking group. Simultaneously usable monomers are not particularly limited and may include olefins (such as ethylene, propylene, isoprene, vinyl chloride, or vinylidene chloride); acrylic acid esters (such as methyl acrylate, ethyl acrylate, or 2-etylhexyl acrylate); methacrylic acid esters (such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, or ethylene glycol dimethacrylate); styrene derivatives (such as styrene, divinylbenzene, vinyltoluene, or a-methylstyrene); vinyl ethers (such as methyl vinyl ether); vinyl esters (such as vinyl acetate, vinyl propionate, or vinyl cinnamate); acrylamides (such as N-tert-butyl acrylamide or N-cyclohexyl acrylamide); methacrylamides; and acrylonitrile derivatives. Further, in order to provide lubrication and stain resistance, it is preferable to introduce a polyorganosiloxane skeleton and a perfluoropolyether skeleton into the fluorine containing copolymers. Such skeletons are formed via polymerization of polyorganosiloxane having a terminal group such as an acryl group, a methacryl group, a vinyl ether group, or a styryl group with the above monomers, polymerization of the above monomers with polyorgsanosiloxane having a radical generating group at the terminal or perfluoropolyether, or reaction of polyorganosiloxane having a functional group at the terminal or perfluoropolyether.

The ratio of each of the above monomers employed to from the fluorine containing copolymers prior to crosslinking is preferably 20-70% by mole with respect to the fluorine-containing vinyl monomers, but is more preferably 40-70% by mole and the ratio of monomers to provide a crosslinking group is preferably 1-20% by mole, but is more preferably 5-20% by mole, while the ratio of other monomers used in combination is preferably 10-70% by mole, but is more preferably 10-50% by mole.

It is possible to prepare fluorine-containing copolymers via polymerization in the presence of radical polymerization initiators, employing methods such as solution polymerization, bulk polymerization, emulsion polymerization, or suspension polymerization.

Pre-crosslinking fluorine-containing resins are commercially available. Examples of commercially available pre-crosslinking fluorine-containing resins include SAITOP (produced by Asahi Glass Co.), TEFLON (registered trade name) AF (produced by DuPont), polyvinylidene fluoride, RUMIFRON (produced by Asahi Glass Co.), and OPSTAR (produced by JSR).

The Dynamic friction factor and the contact angle to water of the low refractive index layer containing crosslinked fluorine-containing resins are preferably in the range of 0.03-0.15 and 90-120 degrees, respectively.

<Additives>

Additives such as silane coupling agents or hardeners may be contained in the low refractive index layer coating solution, if desired. Specific examples of the silane coupling agents include vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and 3-(2-aminoethylaminopropyl)trimethoxysilane.

Cited as hardeners are organic acid metal salts such as sodium acetate or lithium acetate, of which sodium acetate is particularly preferred. The addition amount to the siliconalkoxysilane hydrolyzed solution is preferably in the range of approximately 0.1-1 part by weight with respect to 100 parts by weight of solids in the hydrolyzed solution.

Various leveling agents, surfactants, or low surface tension substances such as silicone oil and the like are also added into the low refractive index layer coating solution employed in the present invention.

Specific examples of commercially available silicone oils include L-45, L-9300, FZ-3704, FZ-3703, FZ-3720, FZ-3786, FZ-3501, FZ-3504, FZ-3508, FZ-3805, FZ-3707, FZ-3710, FZ-3750, FZ-3760, FZ-3785, FZ-3785 and Y-7400 (produced by Nippon Unicar Co., Ltd.), and KF96L, KF96, KF96H, KF99, KF54, KF965, KF968, KF56, KF995, KF351, KF352, KF353, KF354, KF355, KF615, KF618, KF945, KF6004 and FL100 (produced by Shin-Etsu Chemical Co., Ltd.).

Coatability to a substrate or a lower layer is enhanced by these components. When they are added into the uppermost layer of the multilayer, not only water repellency, oil repellency and anti-stain property are enhanced, but also the surface-abrasion resistance is improved. Since the excessive addition of these components results in repellency during coating, it is preferred that the addition amount is within the range of 0.01-3% by weight with respect to the solid content in the coating solution.

<Solvents>

Solvents employed in the coating solution during coating the low refractive index layer include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, or butanol; ketones such as acetone, methyl ethyl ketone, or cyclohexanone; aromatic hydrocarbons such as benzene, toluene, or xylene; glycols such as ethylene glycol, propylene glycol, or hexylene glycol; glycol ethers such as ethyl cellosolve, butyl cellosolve, ethyl CARBITOL, butyl CARBITOL, diethyl cellosolve, diethyl CARBITOL, or propylene glycol monomethyl ether; N-methylpyrrolidone, dimethylformamide, methyl lactate, ethyl lactate, methyl acetate, and water. These may be employed singly or in combinations of at least two types.

<Coating Methods>

The low refractive index layer is coated employing the methods known in the art, such as dipping, spin coating, knife coating, bar coating, air doctor coating, curtain coating, spray costing, or die coating, as well as ink-jet methods known in the art. Coating methods which enable continuous coating and thin layer coating are preferably employed. The coated amount is commonly 0.1-30 μm in term of wet thickness, but is preferably 0.5-15 μm. The coating rate is preferably 10-80 m/minute.

When the composition of the present invention is coated onto a substrate, it is possible to control layer thickness and coating uniformity by regulating the solid concentration in the coating solution and the coated amount.

In the present invention, it is also preferable to form an anti-reflection layer composed of a plurality of layers in such a manner that the medium refractive index layer and high refractive index layer, described below, are provided.

The structure examples of the antireflection layer usable in the present invention are described below, but the antireflection layer is not limited thereto.

Long-length film/hard coat layer/low refractive index layer

Long-length film/hard coat layer/medium refractive index layer/low refractive index layer

Long-length film/hard coat layer/medium refractive index layer/low refractive index layer

Long-length film/hard coat layer/high refractive index layer/low refractive index layer

Long-length film/hard coat layer/medium refractive index layer/high refractive index layer/low refractive index layer

Long-length film/antistatic layer/hard coat layer/medium refractive index layer/high refractive index layer/low refractive index layer

Long-length film/hard coat layer/anti-static layer/ medium refractive index layer/high refractive index layer/low refractive index layer

Anti-static layer/long-length film/hard coat layer/medium refractive index layer/high refractive index layer/low refractive index layer

Long-length film/hard coat layer/high refractive index layer/low refractive index layer/high refractive index layer/low refractive index layer

(Medium Refractive Index Layer and High Refractive Index Layer)

The constituting components of the medium and high refractive index layers are not particularly limited as long as the specified refractive index layer is prepared. However, it is preferable that the above layer is composed of the following metal oxide particles at a high refractive index, and binders. Other additives may be incorporated. The refractive index of the medium refractive index layer is preferably 1.55-1.75, while that of the high refractive index layer is preferably 1.75-2.20. The thickness of the high and medium refractive index layers is preferably 5-1000 nm, is more preferably 10-200 nm, but is most preferably 30-100 nm. It is possible to coat those layers employing the same coating method as that of the above low refractive index layer.

<Metal oxide particles>

Metal oxide particles are not particularly limited. For example, employed as a main component may be titanium dioxide, aluminum oxide (alumina), zirconium oxide (zirconia), zinc oxide, antimony-doped tin oxide (ATO), antimony pentaoxide, indium-tin oxide (ITO), and iron oxide, which may be blended. In the case of use of titanium dioxide, in term of retardation of activity of photocatalysts, it is preferably to employ metal oxide particles having a core/shell structure, which are prepared in such a manner that titanium oxide is employed as a core and the core is covered with a shell composed of alumina, silica, zirconia, ATO, ITO, or antimony pentaoxide.

The refractive index of metal oxide particles is preferably 1.80-2.60, but is more preferably 1.90-2.50. The average diameter of the primary particles of the metal oxide particles is preferably 5-200 nm, but is more preferably 10-150 nm. When the particle diameter is excessively small, metal oxide particles tend to aggregate to degrade dispersibility, while when it is excessively large, haze is undesirably increased. Inorganic particles are preferably in the form of rice grain, needle, sphere, cube, or spindle, or amorphous.

Metal oxide particles may be surface-treated with organic compounds. Examples of such organic compounds include polyol, alkanolamine, stearic acid, silane coupling agents, and titanate coupling agents. Of these, most preferred are silane coupling agents, described below. At least two types of surface treatments may be combined.

It is possible to prepare high and medium refractive index layers exhibiting desired refractive indices via appropriate selection of the type of metal oxides and the addition ratio thereof.

<Binder>

Binders are incorporated to improve film forming properties and physical properties of a coating. Employed as such binders may, for example, be the aforesaid ionizing radiation curing type resins, acrylamide derivatives, multifunctional acrylates, acrylic resins, and methacrylic resins.

(Metal Compound and Silane Coupling Agent)

Incorporated as other additives may be metal compounds and silane coupling agents, which may be employed as a binder.

Employed as the metal compounds may be the compounds represented by Formula (6) or chelate compounds thereof. AnMBx-n  Formula (6)

wherein M represents a metal atom; A represents a hydrolysable functional group or a hydrocarbon group having a hydrolysable functional group; B represents a group of atoms, which covalently or ionically bonds metal M; x represent valence of metal atom M; and n represents an integer of 2-x.

Examples of hydrolysable functional group A include an alkoxyl group, a halogen atom such as a chorine atom, an ester group, and an amido group. Preferred as the compounds represented by above Formula (6) are alkoxides having at least two alkoxyl groups bonding a metal atom, or chelate compounds thereof. In view of refractive index, reinforcing effects of coating strength, and ease of handling, cited as preferred metal compounds are titanium alkoxides, zirconium alkoxides, and silicon alkoxides, or chelate compounds thereof. Titanium alkoxides exhibits a high reaction rate, a high refractive index, and ease of handling. However, its excessive addition degrades lightfastness due to its photocatalytic action. Zirconium akloxides exhibit a high refractive index, but tends to result in cloudiness, whereby careful dew point management is required during coating. On the other hand, silicon alkoxides exhibit a low reaction rate and a low refractive index, but ease of excellent handling and excellent lightfastness. Silane coupling agents can react with both inorganic particles and organic polymers, whereby it is possible to prepare a strong coating. Further, titanium aloxides enhance reaction with ultraviolet radiation curing resins and metal alkoxides, whereby it is possible to enhance physical characteristics of a coating even by a small amount of their addition.

Examples of titanium alkoxides include tetramethoxytitaium, tetraethoxytitanium, tetra-iso-propoxytitanium, tetra-n-propoxytitanium, tetr-n-butoxytitanium, tetra-sec-butoxytitanium, and tetra-tert-butoxytitanium.

Examples of zirconium alkoxides include tetramethoxyzirconium, tetraethoxyzirconium, tetra-iso-propoxyzirconium, tetra-n-proxyzirconium, tetra-n-butoxyzirconium, tetra-sec-butoxyzirconium, and tetra-tert-butoxyzirconium.

Silicon alkoxides and silane coupling agents are the compounds represented by following Formula (7). RmSi(OR′)n  Formula (7) wherein R represents a reactive group such as an alkyl group (preferably an alkyl group having 1-10 carbon atoms), a vinyl group, a (meth)acryloyl group, an epoxy group, an amido group, a sulfonyl group, a hydroxyl group, a carboxyl group, or an alkoxyl group, R′ represents an alkyl group (preferably an alkyl group having 1-10 carbon atoms), and m+n is 4.

Specifically cited are tetramethoxysilane, tetraethoxysilane, tetra-iso-propoxysilane, tetra-n-propoxysilane, tetra-n-butoxysilane, tetra-sec-butoxysilane, tetra-tert-butoxysilane, terapentaethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriproxysilane, methyltributoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, hexyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and 3-(2-aminoethylaminopropyl)trimethoxysilane.

Cited as preferred chelating agents which are allowed to coordinate with a free metal compound to form a chelate compound may be alkanolamines such as diethanolamine or triethanolamine; glycols such acetylene glycol, diethylene glycol, or propylene glycol; and acetylacetone, ethyl acetacetate, having a molecular weight of at most 100,000. By employing such chelating agents, it is possible to prepare chelate compounds which are stable for water mixing and exhibit excellent coating strengthening effects.

In the medium refractive index composition, the addition amount of the metal compounds is preferably less than 5% by weight in terms of metal oxides, while in the high refractive index composition, the same is preferably less than 20% by weight in terms of metal oxides.

(Polarizing Plate)

An optical film of the present invention is useful as a polarizing plate protective film, and the polarizing plate can be produced by the general method. The back sides of the optical films of the present invention are subjected to alkaline saponification, and are preferably bonded onto at least one of the surfaces of the polarizing film produced by immersion in iodine solution, using a fully saponifiable aqueous solution of polyvinyl alcohol. The foregoing film or another polarizing plate protective film may be used on the other surface. The commercially available cellulose ester film (e.g. Konica Minoltatac KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5 by Konica Minolta Opto, Inc.) is preferably used. For the optical film of the present invention, the polarizing plate protective film used on the other surface preferably has the in-plane retardation Ro of 30-300 nm at 590 nm and Rt of 70-400 nm in phase difference. For example, the methods disclosed in Japanese Patent O.P.I Publication Nos. 2002-71957 and 2003-170492 can be used for production. Further, for example, preferably employed is a polarizing plate protective film in which retardation values Ro and Rt are −15 nm≦Ro≦15 nm and −15 nm−Rt≦15 nm, respectively, prepared in the method described in Japanese Patent O.P.I Publication No. 2003-12859. It is also preferred to use the polarizing plate protective film also serving as an optical compensating film having an optically anisotropic layer formed by orienting a liquid crystal compound such as a discotheque liquid crystal. For example, the optically anisotropic layer can be formed by the method disclosed in Japanese Patent O.P.I Publication No. 2003-98348. A polarizing plate characterized by excellent flatness and stable effect of widening the angle of visibility can be manufactured by combined use with the optical film of the present invention.

The polarizing film as a major constituent of the polarizing plate is a device that permits passage of only the light of the polarizing surface in a predetermined direction. The currently known typical polarizing film is a polyvinyl alcohol based polarizing film. The polyvinyl alcohol based film dyed by iodine and that dyed by dichromatic dyes are available. The polarizing film to be used is produced as follows: The aqueous solution of polyvinyl alcohol is used to form a film, which is dyed and is uniaxially oriented. Alternatively, the film is uniaxially orientated subsequent to dyeing and is preferably subjected to durability treatment using a boric acid compound. It is preferable that the polarizing film has a thickness of 5-30 μm, and more preferable that it has a thickness of 10-20 μm.

Preferably usable is ethylene-modified polyvinyl alcohol having an ethylene unit content of 1-4% by mole, a polymerization degree of 2000-4000 and a saponification ratio of 99.0-99.99% by mole, described in Japanese Patent O.P.I. Publication Nos. 2003-248123 and 2003-342322. Of these, an ethylene-modified polyvinyl alcohol film having a hot-water cutting temperature of 66-73° C. is preferably usable. In order to decrease color spots, it is further preferable that the difference of the hot-water cutting temperature between two points at a distance of 5 cm in the TD direction is at most 1° C. In order to decrease color spots, it is still more preferable that the difference of the hot water cutting temperature between two points at a distance of 1 cm in the TD direction is at most 0.5° C.

A polarizing plate with this ethylene-modified polyvinyl alcohol film exhibits excellent polarization performance and durability, accompanied with decreased color spots, and is preferably employed particularly for a large-size liquid crystal display device.

A polarizing plate protective film or polarizing plate protective films generally adhere(s) to one surface or both surfaces of a polarizing plate to utilize a polarizing plate prepared as described above as a polarizing plate. PVA based adhesives, urethane based adhesives and so forth, which are usable during adhesion, are provided, but of these, the PVA based adhesives are preferably usable.

(Display Apparatus)

When the polarizing plate used for an optical film in the present invention is built in the display apparatus, a wide variety of display apparatuses characterized by excellent visibility can be produced. The optical film of the present invention is preferably used in the reflection, transparent and translucent LCDs or in the LCDs based on a wide variety of drive methods such as TN, STN, OCB, HAN, VA (PVA and MVA) and IPS methods. The optical film of the present invention are characterized by distinguished flatness and are preferably used in a wide variety of display apparatuses including plasma display, field emission display, organic EL display, inorganic EL display and electronic paper. Particularly, the display apparatus having a large screen size such as 30 inch model or greater, especially in the range of 30-54 inch model is free of any white patch on the peripheral area. The effect can be maintained for a long time. A remarkable effect is observed in the model MVA liquid crystal display. Especially, elimination of uneven color arrangement, glitter or wavy unevenness as an object of the present invention is achieved. Thus, user's eyes are not adversely affected after long-time viewing.

EXAMPLE

Next, the present invention will be explained employing examples, but the present invention is not limited thereto.

Example 1

<Preparation of Cellulose Ester Films 1-3>

-   (Silicon dioxide dispersion A) 12 parts by weight -   Aerogil 972V (produced by Nihon Aerogil Co., Ltd.) -   (primary particles having an average diameter of 16 nm, and an     apparent specific gravity of 90 g/liter) -   Ethanol 88 parts by weight

The above composition was stirred for 30 minutes using a dissolver and then dispersed by using Manton-Gaulin homogenizer. The turbidity of the resultant dispersion was 200 ppm. To the silicon dioxide dispersion, 88 parts by weight of methylene chloride was added while stirring to prepare diluted silicon dioxide dispersion A.

(Preparation of In-line Adding Liquid A)

-   Tinubin 109 (produced by Ciba Specialty Chemicals Inc.) 11 parts by     weight -   Tinubin 171 (produced by Ciba Specialty Chemicals Inc.) 5 parts by     weight -   Methylene chloride 100 parts by weight

The above composition was charged into a closed vessel, and heated while stirring in order to completely dissolve the composition, and then filtered.

To the resulting solution, 36 parts by weight of the diluted silicone dioxide dispersion A was added while stirring and then further stirred for 30 minutes. After that, 6 parts by weight of cellulose acetate propionate having an acetyl substitution degree of 1.9 and a propionyl substitution degree of 0.8 was added while stirring, and further stirred for 60 minutes, followed by filtering through a polypropylene wound cartridge filter TCW-PPS-1N, manufactured by Advantic Toyo Co., Ltd., to prepare an in-line adding liquid A.

(Preparation of Dope A)

-   Cellulose ester (Cellulose triacetate synthesized with linter     cotton, Mn=148000, Mw=310000, Mw/Mn=2.1, an acetyl substitution     degree of 2.92) 100 parts by weight -   Trimethylolpropanebenzoate 5.0 parts by weight -   Ethylphthalylethylglycolate 5.5 parts by weight -   Methylene chloride 440 parts by weight -   Ethanol 40 parts by weight

The above composition was charged into a closed vessel, and heated while stirring to completely dissolve the composition, followed by filtering with Azumi Filter Paper No. 24, manufactured by Azumi Filter Paper Co., Ltd., to prepare a Dope A.

Dope A was filtered in the film forming line through Finemet NF and in-line adding liquid A was also filtered through Finemet NF, manufactured by Nihon Seisen Co., Ltd., in the course of an in-line adding line. To 100 parts by weight of filtered Dope A, 3 parts by weight of filtered in-line adding liquid A was added and sufficiently mixed by an in-line mixer (Toray static in-line mixer Hi-Mixer SWJ), and then uniformly cast onto a stainless steel belt support having a width of 1.8 m at 32° C. using a belt casting machine. The solvent was evaporated on the stainless steel belt support until the residual solvent decreased to 100% and the web was peeled off from the stainless steel belt support. The solvent was evaporated at 35° C. from the peeled cellulose ester web and the web was slit in to 1.65 m width and then dried at 135° C. while stretching in the ratio of 1.05 times by the tenter in TD direction (direction orthogonal to the transporting direction). The residual solvent amount was 20t when the stretching by tenter was started.

After that, the drying was completed by transporting the web through many rollers in drying zones kept at 110° C. and at 120° C. The dried film was slit into 1.4 m width, and knurling having a width of 1 cm and an average height of 8 μm was provided at both edges of the film. The film was wound on a core having an internal diameter of 6 inches by an initial winding tension of 220 N/m and a final winding tension of 110 N/m to obtain cellulose ester film 1. A stretching factor in MD direction (the same direction as the film transporting direction) immediately after peeling, which is calculated from the rotation speed of the stainless steel belt support and the operating speed of the tenter, was 1.07 times. The average thickness and winding length of cellulose ester film 1 were 40 μm and 3000 m, respectively.

Next, similarly to cellulose ester film 1, cellulose ester film 2 of an average thickness of 60 μm, and cellulose ester film 3 of an average thickness of 80 μm were prepared.

<Treatment of Rubbing a Film Surface with Elastomer Moisturized by Liquid>

Treatment of rubbing a film surface with elastomer moisturized by liquid was conducted with the following specification employing the above-described cellulose ester films 1-3.

One surface of a long-length film was rubbed with elastomer 1 moisturized by liquid employing a film transporting apparatus as shown in FIG. 1.

Material of elastomer: Acrylonitrile-butadiene rubber having a thickness of 5 mm is coated onto an aluminum roller of 20 cm.

Hardness of elastomer: Rubber hardness 30 (measured according to JIS-K-6253 employing a type A durometer)

Size of elastomer: a roll diameter of 20 cm

Variation in friction factor of elastomer: After cleaning the elastomer surface with petroleum benzin, a trichloroisocyanuric acid solution was coated onto the elastomer surface by bringing a waste cloth interpenetrating 5% by weight of the trichloroisocyanuric acid solution dissolved in ethyl acetate ester into contact with the elastomer while rotating the elastomer. This elastomer was dried at room temperature, and the solvent was volatilized in about 30 minutes to dry the surface. The friction factor was changed by varying concentration of the trichloroisocyanuric acid solution as shown in FIG. 1. In addition, the measurement was carried out by the foregoing method employing a Heidon type 14 surface property tester produced by Shinto Scientific Co., Ltd.

The driving direction and the number of revolutions of elastomer: Rotation in the reverse rotation direction with respect to the film transporting direction (the number of revolutions of 10 rpm)

Temperature of elastomer: 30° C.

Transportation speed of a cellulose ester film was 15 m/min.

Pure water was used as liquid. A long nozzle of 140 cm in the form of a rod was placed in the width direction as nozzle 8, and 1 mm of clearance was set to an opening at the end to spray pure water in an amount of solution sending of 30 L/min onto the film surface at the position of nozzle 8 shown in FIG. 1. A commercially available opening of 0.2 mm was usable as filter 10.

When air was supplied onto the back surface of a film employing air nozzle 5, the supplied air pressure was adjusted to 3.0×10² Pa as a film surface pressure applied to elastomer.

In order to wash elastomer employing an ultrasonic transducer, 2 sets of ultrasonic transducers as the special specification device (produced by Alex Corporation) in the film width direction, and 4 sets of ultrasonic transducers in the film transporting direction were arranged to be placed. This ultrasonic transducer has a size of 50 cm in the film width direction and 30 cm in film transporting direction, and an ultrasonic wave of 100 kHz was output by 1000 W in power.

Edge position controllers (EPC) each were placed at 10 m position on the upstream side, as well as on the downstream side from the apparatus to control the position of a long-length film rubbed on elastomer 1.

Employing the above-described cellulose ester films 1-3, spraying of liquid 4 (pure water) conducted or not conducted on the film surface with nozzle 8 and friction factor of elastomer 1, moisturizing time of the treated surface of a long-length film obtained by the film position changed from elastomer 1 to air nozzle 6, air spraying conducted or not conducted on the back surface of a film by air nozzle 5, temperature of pure water 4 (temperature adjusted by a cooler or a heater), and the EPC operation conducted or not conducted, each, were changed as shown in FIG. 1 to prepare treated cellulose ester films c-1-c-25.

(Preparation of Optical Film Having Anti-reflection Layer)

Each of optical films having an anti-reflection layer was prepared employing the above-described cellulose ester films c-1-c-25.

The refractive index of each layer constituting an anti-reflection layer was measured by the following method.

(Refractive Index)

A refractive index of each refractive index layer was determined from a measurement result of spectral reflectance of a spectrophotometer with respect to samples in which each layer was independently coated on a hard coat layer prepared below. The measurement of a reflectance in a visible region (400-700 nm) was performed at a regular reflection at 5 degrees by use of U-4000 Type Spectrophotometer (produced by Hitachi, Ltd.), while the back surface as a measurement surface was subjected to a light absorbing treatment to prevent light reflection by use of a black spray after having been embossing treated.

(Particle Diameter of Metal Oxide Particles)

A particle diameter of utilized metal oxide particles was determined by measuring each 100 particles through an electron microscope (SEM) and calculating the average vale of a diameter of a circle circumscribing each particle as a particle diameter.

<<Formation of Hard Coat Layer>>

A hard coat layer coating solution was prepared by filtering the following hard coat layer coating solution with a polypropylene filter with a pore diameter of 0.4 μm. The prepared coating solution was applied onto the above-described cellulose ester films C-1-C-25, employing a micro-gravure coater, and dried at 90°0 C. Thereafter, the coated layer was cured at an exposure of 0.1 J/cm² under an illuminance of 100 mW/cm² in the exposed portion employing a UV lamp, whereby a hard coat film was prepared by forming a hard coat layer having a dry thickness of 7 μm.

(Hard Coat Layer Coating Solution)

The following materials were mixed while stirring to prepare a hard coat layer liquid coating composition. Acryl monomer, KAYARAD DPHA 220 parts by weight (dipentaerythritol hexaacrylate, produced by Nippon Kayaku Co., Ltd.) IRUGACURE 184 (produced by Ciba  20 parts by weight Specialty Chemicals Inc.) Propylene glycol monomethyl ether 110 parts by weight Ethyl acetate 110 parts by weight <<Preparation of an Optical Film with an Anti-reflection Layer>>

An anti-reflection layer was prepared by applying, in the following order, the high refractive index layer and the low refractive index layer as described below onto the hard coat film prepared as above, whereby optical films 1-25 with a antireflection layer were prepared.

<<Formation of Antireflection Layer: High Refractive Index Layer>>

The following high refractive index layer coating composition was applied onto the hard coat film employing an extrusion coater to result in a cured layer thickness of 78 nm. The coating was dried at 80° C. for one minute, cured via exposure to UV radiation of 0.1 J/cm², and further thermally cured at 100° C. for one minute, whereby a high refractive index layer was prepared.

The refractive index of this high refractive index layer was 1.62.

<High Refractive Index Layer Coating Composition> Metal oxide particle isopropyl alcohol solution  55 parts by weight (ITO particles having a particle diameter of 5 nm and at a solid content of 20%) Metal compound: Ti(OBu)₄(tetra-n- 1.3 parts by weight butoxytitanium Ionizing radiation curable resin: 3.2 parts by weight dipentaerythritol acrylate hexaacrylate)

Photopolymerization initiator: IRUGACURE 184 0.8 part by weight (produced by Ciba Specialty Chemicals Inc.) 10% straight chain dimethylsilicone-EO 1.5 parts by weight block copolymer propylene glycol monomethyl ether liquid composition (FZ-2207, produced by Nippon Unicar Co., Ltd.) Propylene glycol monomethyl ether 120 parts by weight Isopropyl alcohol 240 parts by weight Methyl ethyl ketone 40 parts by weight <<Formation of Antireflection Layer: Low Refractive Index Layer>>

The following low refractive index layer coating composition was applied onto the above high refractive index layer employing an extrusion coater. The coated layer was dried at 100° C. for one minute, cured via exposure to ultraviolet radiation of 0.1 J/cm², wound onto a heat-resistant plastic core to reach a length of 4000 m, and thermally treated at 80° C. for three days, whereby optical films 1-25 with an anti-reflection layer were prepared.

The thickness and refractive index of the resulting low refractive index layer were 95 nm and 1.37, respectively.

(Preparation of Low Refractive Index Layer Coating Composition)

<Preparation of Tetraethoxysilane Hydrolysis Product A>

Hydrolysis product A was prepared in such a manner that 289 g of tetraethoxysilane and 553 g of ethanol were mixed, and the resulting mixture, along with 157 g of a 0.15% aqueous acetic acid solution, was stirred for 30 hours in a water bath at 25° C. Ethoxysilane hydrolysis product A 110 parts by weight Silica based hollow particles (following P-2) 30 parts by weight dispersion KMB503 (Silane coupling agent, produced 4 parts by weight by Shin-Etsu Chemical Co., Ltd.) 10% propylene glycol monomethyl ether liquid 3 parts by weight of straight chain dimethylsilicone-EO block copolymer (FZ-2207, produced by Nippon Unicar Co., Ltd.) Propylene glycol monomethyl ether 400 parts by weight Isopropyl alcohol 400 parts by weight <Preparation of Silica Based Hollow Particle P-2 Dispersion>

A mixture of 100 g of a silica sol at an average particle diameter of 5 nm and a SiO₂ concentration of 20% by weight and 1900 g of pure water was heated to 80° C. The pH of this mother reaction liquid was 10.5. Simultaneously added to the mother liquid were 9,000 g of a 0.98% aqueous sodium silicate solution as SiO₂ and 9,000 g of a 1.02% aqueous sodium aluminate solution as A1 ₂O₃. During the above addition, temperature of the reaction liquid was maintained at 80° C. The pH of the reaction liquid increased to 12.5 immediately after the above addition and subsequently remained nearly the same. After completion of the addition, the reaction liquid was cooled to room temperature and washed via an ultrafiltration membrane, whereby a SiO₂.Al₂O₃ nucleus particle dispersion at a solid concentration of 20% by weight was prepared (Process (a)).

Added to 1700 g of pure water was 500 g of the above nucleus particle dispersion and the resulting mixture was heated to 98° C. While maintaining the above temperature, 3000 g of silicic acid liquid (at a SiO₂ concentration of 3.5% by weight), which was prepared by removing alkali of an aqueous sodium silicate solution employing cation exchange resins, was added, whereby a nucleus particle dispersion, which formed the first silica coated layer, was prepared (Process (b)).

Subsequently, 1125 g of pure water was added to 500 g of the nucleus particle dispersion, which formed the first silica coated layer, resulting in a solid concentration of 13% by weight via cleaning with ultrafiltration membrane. Further, an aluminum removal treatment was performed by reducing the pH to 1.0 via dropwise addition of concentrated hydrochloric acid (at 35.5%). Subsequently, aluminum salts, which were dissolved employing the ultrafiltration membrane, were separated by adding 10 L of an aqueous hydrochloric acid solution at a pH of 3 and 5 L of pure water, whereby a porous SiO₂.Al₂O₃ particle dispersion, in which some of the constituting components of the nucleus particles which formed the first silica coated layer were removed, were prepared (Process (c)).

After heating, to 35° C., a mixture of 1500 g of the above porous particle dispersion, 500 g of pure water, 1750 g of ethanol, 626 g of 28% ammonia water, and 104 g of ethyl silicate (SiO₂ at 28% by weight) was added, and a second silica coated layer was formed by coating the surface of the porous particles formed in the first silica coated layer with the hydrolysis polycondensation product of ethyl silicate. Subsequently, silica based hollow particles (P-2) at a solid concentration of 20% in which the solvent was replaced with ethanol was prepared employing an ultrafiltration membrane.

The thickness of the first silica coated layer of the above silica based particles was 2 nm, the average particle diameter was 47 nm, Mox/SiO₂ (mol ratio) was 0.0017, and the refractive index was 1.28. The average particle diameter was determined employing a dynamic light scattering method. ps <<Evaluation>>

The following evaluation was conducted employing optical films 1-25 with the resulting anti-reflection layer.

(Evaluation of Longitudinal Streaks of Anti-reflection Layer)

Each of 10 optical films having a length of 3000 m with the resulting anti-reflection layers is coated, and sampling was carried out for 1 m² of each winding. A back surface of an anti-reflection layer in the sampling base was blacked out by a black spray, and the number of longitudinal streaks were evaluated via visual evaluation of the anti-reflection layer surface employing three wavelength fluorescent lamps. (10 windings×1 m² ×10 positions=100 m² for evaluation)

Longitudinal streaks generated in the film transporting direction are straight streaks, and color of reflected light at the streak portion is differently observed in comparison to that at the other portion.

A: No occurrence of longitudinal streak

B: Occurrence of one longitudinal streak per 100 m²

C: Occurrence of 2-10 longitudinal streaks per 100 m²

D: Occurrence of more than 10 longitudinal streaks per 100 m²

(Evaluation of Chatter of Anti-reflection Layer)

Each of 10 optical films having a length of 3000 m with the resulting anti-reflection layers is coated, and sampling was carried out for 1 m² of each winding. A back surface of an anti-reflection layer in the sampling base was blacked out by a black spray, and the chatter was evaluated via visual evaluation of the anti-reflection layer surface employing three wavelength fluorescent lamps. (10 windings×1 m²×10 positions=100 m² for evaluation)

Chatter is generated in the film width direction, and each different steapwise color of reflected light is observed. The stepwise pitch is 1-5 mm.

A: No occurrence of chatter

B: Occurrence of chatter in at most 1 m² per 100 m²

C: Occurrence of chatter in more than 1-at most 10 m² per 100 m²

D: Occurrence of chatter in more than 10-at most 20 m2 per 100 m²

(Comet)

Each of 10 optical films having a length of 4000 m with the resulting anti-reflection layers is coated, and sampling was carried out for 1 m² of each winding. A back surface of an anti-reflection layer in the sampling base was blacked out by a black spray, and the comet was evaluated via visual evaluation of the anti-reflection layer surface employing three wavelength fluorescent lamps. (10 windings×1 m²×10 positions=100 m² for evaluation)

The comet means failure caused by repelling of a coating solution employed for an anti-reflection layer, and there are one having a nucleus generated by a foreign matter, and also another one having no nucleus generated by other than a foreign matter.

The above-described coating solution is repelled so as to flow in the film transporting direction, and the length of the repelled film transporting direction results frequently in 10-100 μm.

A: No comet per 100 m²

B: 1-5 comets per 100 m²

C: 6-20 comets per 100 m²

D: More than 20 comets per 100 m²

(Foreign Matter Failure)

Observed were foreign matters per 1 m² resulting in failure generated by projections or depressions having a diameter of at least 100 μm and less than 150 μm, or at least 150 μm via visual examination of a coated layer.

The failure of a foreign matter having a diameter of 100 μm means failure in which a diameter in the case of observing the area of protrusion failure portions and/or depression failure portions as a roughly equivalent circle is 100 μm, when a ratio of thickness variation of a coated layer to the reference surface is at least 2 μm (thickness variation of a coated layer)/100 μm (distance on the reference surface), and the thickness of a coated layer to be changed is at least 0.5 μm, and this is seen as visually observed failure of foreign matters having a size of 100 μm. In the actual foreign matter failure examination, employing samples of the foregoing failure of foreign matters having a size of 100 μm and failure of foreign matters having a size of 150 μm, failure of foreign matters having an intermediate size between a sample of failure of foreign matters having a size of 100 μm and a sample of failure of foreign matters having a size of 150 μm was counted as the number of foreign matters having a diameter of 100-150 μm. Similarly to a sample of failure of foreign matters having a size of 150 μm, failure of foreign matters having not less than this size was counted as foreign matters having a size of at least 150 μm.

The cross-sectional configuration concerning failure generated by projections or depressions can be observed by an optical interferotype surface roughness meter.

Counted foreign matters as indicated above were evaluated according to the following criteria.

A: No foreign matter having a size of at least 100 μm observed.

B: Foreign matters having a size of from 100 μm to less than 150 μm are slightly observed.

C: Foreign matters having a size of from 100 μm to less than 150 μm are observed.

D: Not only foreign matters having a size of from 100 μm to less than 150 μm, but also foreign matters having a size of at least 150 μm are observed.

(Generation of Wrinkles)

During transporting each of treated 10 cellulose ester films, whether or not wrinkles are generated was visually observed, and evaluated according to the following criteria.

A: No generation of wrinkles is observed in 10 films.

B: Generation of wrinkles is slightly observed in 1-3 films.

C: Generation of wrinkles is clearly observed in 1-3 films.

D: Generation of wrinkles is clearly observed in at least 4 films.

The evaluation results are shown in Table 1. TABLE 1 Cellulose ester film Elastomer Thick- Static Effects ness friction Treatment condition Chatter Com- Foreign Re- *1 *2 No. (μm) factor *3 *4 *5 *6 *7 *8 *9 failure et matter Wrinkle marks 1 C-1 1 40 0.15 ** **  30 sec 30 ** ** B D B B D Comp. 2 C-2 1 40 0.2 ** **  30 sec 30 ** ** B B B B B Inv. 3 C-3 1 40 0.3 ** **  30 sec 30 ** ** B B B B B Inv. 4 C-4 1 40 0.5 ** **  30 sec 30 ** ** B B B B B Inv. 5 C-5 1 40 0.7 ** **  30 sec 30 ** ** A A B B B Inv. 6 C-6 1 40 0.9 ** **  30 sec 30 ** ** A A B B B Inv. 7 C-7 1 40 1.1 ** **  30 sec 30 ** ** B D B B D Comp. 8 C-8 1 40 0.7 ** **  1 sec 30 ** ** B B C C C Inv. 9 C-9 1 40 0.7 ** **  2 sec 30 ** ** B B B B B Inv. 10 C-10 1 40 0.7 ** **  60 sec 30 ** ** B B B B B Inv. 11 C-11 1 40 0.7 ** **  65 sec 30 ** ** B B B C C Inv. 12 C-12 1 40 0.7 ** Not** 100 sec 30 ** ** B B B C C Inv. 13 C-13 1 40 0.7 ** **  30 sec 25 ** ** B B C C C Inv. 14 C-14 1 40 0.7 ** **  30 sec 50 ** ** A A A A A Inv. 15 C-15 1 40 0.7 ** **  30 sec 70 ** ** A A A A A Inv. 16 C-16 1 40 0.7 ** **  30 sec 100 ** ** A A A A A Inv. 18 C-18 1 40 0.7 Not** **  30 sec 50 ** ** B B B C C Inv. 19 C-19 1 40 0.7 ** **  30 sec 50 ** ** A A A A A Inv. 20 C-20 2 60 0.7 ** **  30 sec 50 ** ** A A A A A Inv. 21 C-21 3 80 0.7 ** **  30 sec 50 ** ** A A A A A Inv. 22 C-22 2 60 0.7 ** **  30 sec 50 Not** Not** B B B B B Inv. 23 C-23 1 40 No treatment ** D D D D D Comp. 24 C-24 2 60 No treatment ** D D D D D Comp. 25 C-25 3 80 No treatment ** D D D D D Comp. **Conducted, *1 Optical film No. with an anti-reflection layer *2 Treated cellulose ester film No., *3 Spraying of liquid ** or Not** on the film surface with nozzle 8, Comp.: Comparative example, Inv.: Present invention *4 Removing of liquid ** or Not** on the film surface with air nozzle 6 *5 Moisturizing time of a film, *6: Liquid temperature of pure water (° C.) *7 Air spraying ** or Not** on the back surface of a film with air nozzle 5 *8: EPC operation conducted or not conducted, *9: Longitudinal streak failure

As is clear from Table 1, it is to be understood that optical films 2-6 and 8-22 with an anti-reflection layer, employing treated cellulose ester films C-2-C-6 and C-8-C-22 exhibit improved properties concerning longitudinal streak failure, chatter failure, comet, foreign matter failure and wrinkles in comparison to those of comparative examples. It is also to be understood that the above-described improving effects are further enhanced by setting each of treatment methods described in Structures 2-9 in a desired range.

Example 2

Polarizing plates and liquid crystal displays were prepared employing optical films 1-25 with an anti-reflection layer, produced in Example 1.

<Preparation of Polarizing Plate>

A 120 μm thick polyvinyl alcohol film was uniaxially stretched (at 110° C. and a stretching factor of 5 times). The stretched film was immersed into an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water for 60 seconds, and subsequently immersed into an aqueous solution at 68° C. consisting of 6 g of potassium iodide, 7.5 g of boric acid, and 100 g of water. The resulting film was washed and dried, whereby a polarizing film was prepared.

Subsequently, based on the following Processes 1-5, polarizing plates were prepared by sticking together a polarizing film, optical films 1-25 with an anti-reflection layer prepared in Example 1 and a cellulose ester film as a polarizing plate protective film on the back surface side. A cellulose ester film (Konica Minolta Tac KC8UCR-5, produced by Konica Minolta Opt, Inc.) having a phase difference is used for the polarizing plate protective film on the back surface side to prepare each of polarizing plates.

Process 1: An optical film with an anti-reflection layer was immersed into a 2 mol/L sodium hydroxide solution at 60° C. for 90 seconds then washed with water, whereby an optical film with an anti-reflection layer which underwent saponification on the side adhered to a polarizer was prepared.

Process 2: The above polarizing film was immersed for 1-2 seconds in an adhesive vessel of polyvinyl alcohol of a solid content of 2% by weight.

Process 3: The excessive adhesive adhered to the polarizing film in process 2 was wiped off and the polarizing film was arranged on the optical film with an anti-reflection layer treated in process 1.

Process 4: The resulting optical film with an anti-reflection layer laminated in process 3, the polarizer, and the cellulose ester on the back side were allowed to adhere at a conveying rate of about 2 m/minute under a pressure of 20-30 N/cm².

Process 5: In a drier at 80° C., each of the samples prepared by allowing a polarizing film prepared in process 4, each optical film with an anti-reflection layer, and each cellulose ester film on the back surface side to adhere together was dried for two minutes, whereby each polarizing Plate was prepared. Polarizing plates 1-25 were prepared employing optical films 1-25 with an anti-reflection layer.

<<Preparation of Liquid Crystal Displays>>

A liquid crystal panel employed for viewing angle measurement was prepared as described below, and characteristics as a liquid crystal display were evaluated.

The both-sided polarizing plate, in advance, adhered to a 15 inch display VL-15OSD, produced by Fujitsu, was peeled off and each of above-described polarizing plates 1-25 was adhered to the glass surface of the liquid crystal cell.

During the above operation, the direction of adhesion of a polarizing plate is arranged so as to make each absorption axis to direct in the same direction as that of the polarizing plate adhered in advance to prepare liquid crystal displays 1-25.

As described above, the following evaluation was conducted employing the resulting liquid crystal displays 1-25.

<<Evaluation>>

<<Evaluation of Visibility>>

Each of the liquid crystal displays, prepared as above, was allowed to stand at 60° C. and 90% RH for 100 hours. Thereafter, the ambience was returned to 23° C. and 55% RH. When the surfaces of the display devices were observed, it was noted that those employing optical films 2-6 and 8-22 with a anti-reflection layer of the present invention exhibited excellent flatness, resulting in an evaluation result of A or B while comparative display devices exhibited wavy unevenness, resulting in an evaluation result of C or D, whereby eyes were inclined to get tired when viewed over a long duration.

A: no wavy unevenness was observed on the surface.

B: Wavy unevenness was slightly observed on the surface.

C: Fine wavy unevenness was somewhat observed on the surface.

D: Fine wavy unevenness was clearly observed on the surface.

[Effect of the Invention]

The present invention makes it possible to provide a method of treating an optical film wherein coating defects such as chatter, coating streaks and comet which are easily caused when coating a functional layer such as an anti-reflection layer on a long-length film are improved, as well as an apparatus of treating an optical film, and it is a feature that chatter can be particularly improved.

There has been known a technology to conduct dust-removing on a film surface to improve a point defect and streaks which are caused by foreign materials, and dust-removing treatment of a wet mode that is close to the present invention is disclosed in each of Japanese Patent O.P.I. Publication Nos. 8-89920, 2001-38306 and 2003-82551362002-182005.

However, the dust-removing treatment is not sufficient although a point defect and streaks which are caused by foreign materials are improved to a certain extent, and chatter was not improved. The present invention can improve both coating defects caused by foreign materials and chatter. 

1. A method of treating an optical film comprising the steps of: (a) rubbing a long-length film transported with elastomer moisturized with liquid; and (b) removing the liquid on a surface of the long-length film, wherein an elastomer surface has a static friction of 0.2-0.9.
 2. The method of claim 1, wherein the elastomer is a surface-modified rubber.
 3. The method of claim 1, further comprising a step of adjusting a transporting position by detecting an end position of width of the long-length film.
 4. The method of claim 1, wherein a temperature of the liquid is in a range of 30-100° C., and a temperature of the elastomer is in a range of 30-100° C.
 5. The method of claim 1, wherein the long-length film is rubbed with the elastomer while pressing a back surface of the long-length film.
 6. The method of claim 1, wherein before the long-length film is rubbed with the elastomer moisturized with the liquid, a treated surface of the long-length film is moisturized with liquid in advance.
 7. The method of claim 6, wherein the treated surface is moisturized with a device of supplying liquid onto the treated surface of the long-length film.
 8. The method of claim 6, further comprising a step of supplying liquid between the long-length film and the elastomer.
 9. The method of claim 1, wherein a period of time during which the treated surface is moisturized is in a range of 2-60 sec.
 10. The method of claim 1, wherein the long-length film has a thickness of 30-70 μm.
 11. An apparatus of treating an optical film comprising a device of rubbing a long-length film transported with elastomer moisturized with liquid, and a device of removing the liquid on a surface of the long-length film, wherein an elastomer surface has a static friction of 0.2-0.9.
 12. The apparatus of claim 11, further comprising a device of adjusting a transporting position by detecting an end position of width of the long-length film.
 13. The apparatus of claim 11, further comprising a device of adjusting a temperature of the liquid to 30-100° C. and a device of adjusting a temperature of the elastomer to 30-100° C.
 14. The apparatus of claim 11, further comprising a device of pressing a back surface of the long-length film.
 15. The apparatus of claim 11, further comprising a device of moisturizing a treated surface of the long-length film with liquid in advance before rubbing the long-length film.
 16. The apparatus of claim 15, wherein the device of moisturizing the treated surface is a device of supplying liquid onto the treated surface of the long-length film.
 17. The apparatus of claim 15, wherein the device of moisturizing the treated surface is a device of supplying liquid between the long-length film and the elastomer.
 18. The apparatus of claim 11, wherein a treating time between a starting point of moisturizing the treated surface with a device of moisturizing the treated surface and a termination point of removing the liquid with a device of removing the liquid is in a range of 2-60 sec.
 19. A method of manufacturing an optical film, comprising a step of coating a functional layer onto the treated surface of the long-length film after conducting treatment via the method of claim
 1. 20. The method of claim 19, wherein the functional layer is an anti-reflection layer or an actinic radiation curable resin layer.
 21. The method of claim 20, wherein the long-length film is a cellulose ester film, and the liquid is water. 